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Long-Term Debt - Additional Information (Detail) (USD $)
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9 Months Ended | 12 Months Ended | 12 Months Ended | 1 Months Ended | 9 Months Ended | 12 Months Ended | 9 Months Ended | 12 Months Ended | 12 Months Ended | 1 Months Ended | 3 Months Ended | 1 Months Ended | 12 Months Ended | 12 Months Ended | 1 Months Ended | 9 Months Ended | 12 Months Ended | 1 Months Ended | 12 Months Ended | 3 Months Ended | 12 Months Ended | 1 Months Ended | 9 Months Ended | |||||||||||||||||||||||||||||||||||||
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Sep. 30, 2012
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Dec. 31, 2012
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Dec. 31, 2010
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Sep. 30, 2013
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Dec. 14, 2012
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Dec. 31, 2011
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May 31, 2008
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Dec. 31, 2012
2.125% Convertible Senior Notes, due July 2012 Repayment of Debt [Member]
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Sep. 30, 2012
2.125% Convertible Senior Notes, due July 2012 Repayment of Debt [Member]
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Jul. 05, 2007
2.125% Convertible Senior Notes, due July 2012 Repayment of Debt [Member]
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Dec. 14, 2012
Secured Debt [Member]
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Apr. 30, 2011
Secured Debt [Member]
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Sep. 30, 2013
Secured Debt [Member]
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Dec. 31, 2012
Secured Debt [Member]
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Dec. 31, 2011
Secured Debt [Member]
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May 15, 2008
Secured Debt [Member]
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Sep. 30, 2013
Revolving Credit Facility [Member]
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Dec. 31, 2012
Revolving Credit Facility [Member]
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Dec. 31, 2011
Revolving Credit Facility [Member]
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Dec. 31, 2012
Existing Credit Agreement [Member]
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Jul. 30, 2013
Unsecured Debt [Member]
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Jul. 19, 2013
Subsequent Event [Member]
Unsecured Debt [Member]
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Apr. 18, 2013
ITS [Member]
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Sep. 30, 2013
ITS [Member]
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Jul. 30, 2013
Unsecured Debt [Member]
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Dec. 31, 2012
Maximum [Member]
Revolving Credit Facility [Member]
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Dec. 31, 2012
Minimum [Member]
Revolving Credit Facility [Member]
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Dec. 31, 2012
9.125% Senior Notes, due April 2018 ( issued march 22, 2010) [Member]
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Dec. 31, 2011
9.125% Senior Notes, due April 2018 ( issued march 22, 2010) [Member]
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Mar. 22, 2010
9.125% Senior Notes, due April 2018 ( issued march 22, 2010) [Member]
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Dec. 31, 2012
9.625% Senior Notes due 2013 [Member]
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Dec. 31, 2012
Senior secured revolving credit facility (Revolver) [Member]
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Apr. 30, 2012
9.125% Senior Notes, due April 2018 (Issued April 25, 2012) [Member]
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Sep. 30, 2013
9.125% Senior Notes, due April 2018 (Issued April 25, 2012) [Member]
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Dec. 31, 2012
9.125% Senior Notes, due April 2018 (Issued April 25, 2012) [Member]
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Apr. 25, 2012
9.125% Senior Notes, due April 2018 (Issued April 25, 2012) [Member]
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Dec. 31, 2011
9.125% Senior Notes, due April 2018 (Issued April 25, 2012) [Member]
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May 31, 2012
2.125% Convertible Senior Notes due July 2012 [Member]
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Dec. 31, 2012
2.125% Convertible Senior Notes due July 2012 [Member]
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May 09, 2012
2.125% Convertible Senior Notes due July 2012 [Member]
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Sep. 30, 2012
2.125% Convertible Senior Notes due July 2012 [Member]
2.125% Convertible Senior Notes, due July 2012 Repayment of Debt [Member]
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Dec. 31, 2012
2.125% Convertible Senior Notes, due July 2012 [Member]
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Jul. 15, 2012
2.125% Convertible Senior Notes, due July 2012 [Member]
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Dec. 31, 2011
2.125% Convertible Senior Notes, due July 2012 [Member]
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Sep. 30, 2013
Term Note [Member]
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Dec. 31, 2012
Term Note [Member]
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Dec. 31, 2011
Term Note [Member]
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Dec. 31, 2012
Term Note [Member]
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Dec. 31, 2011
Term Note [Member]
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Dec. 14, 2012
Term Note [Member]
Secured Debt [Member]
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May 31, 2008
Term Note [Member]
Secured Debt [Member]
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Sep. 30, 2013
7.50% Senior Notes, due August 2020 [Member]
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Jul. 30, 2013
7.50% Senior Notes, due August 2020 [Member]
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Dec. 31, 2012
7.50% Senior Notes, due August 2020 [Member]
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Apr. 18, 2013
Goldman Term Loan [Member]
Secured Debt [Member]
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Sep. 30, 2013
Term Note Due April 2018 [Member]
ITS [Member]
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Jul. 30, 2013
Term Note Due April 2018 [Member]
ITS [Member]
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Sep. 30, 2013
9.125% Senior Notes, due April 2018 [Member]
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Dec. 31, 2012
9.125% Senior Notes, due April 2018 [Member]
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Mar. 22, 2010
9.125% Senior Notes, due April 2018 [Member]
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| Debt Instrument [Line Items] | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Debt premium | $ 4,200,000 | $ 5,000,000 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| 2013 | 11,000,000 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| 2014 | 10,900,000 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| 2015 | 10,800,000 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| 2016 | 10,700,000 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| 2017 and thereafter | 435,800,000 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Aggregate principal amount | 125,000,000 | 300,000,000 | 125,000,000 | 125,000,000 | 125,000,000 | 225,000,000 | 125,000,000 | 300,000,000 | ||||||||||||||||||||||||||||||||||||||||||||||||||||
| Percentage of notes guaranteed by restricted subsidiaries | 2.125% | 9.125% | 9.125% | 9.625% | 9.125% | 9.125% | 2.125% | 2.125% | 2.125% | 7.50% | 7.50% | 7.50% | 9.125% | 9.125% | ||||||||||||||||||||||||||||||||||||||||||||||
| Repayments of debt | 225,000,000 | 42,000,000 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Par value of senior notes | 104.00% | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Gross proceeds of aggregate principal amount additional issued | 130,000,000 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Repurchase of Convertible senior notes | 122,900,000 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Notes paid off | 2,100,000 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Debt issuance costs | 5,400,000 | 11,600,000 | 11,600,000 | 3,600,000 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Debt issuance cost, Net of amortization | 8,100,000 | 7,600,000 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Percentage of the aggregate principal amount redeemed | 35.00% | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Percentage of redemption price before notice | 109.125% | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Percentage of redemption price after notice | 104.563% | 104.563% | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Percentage of repurchase | 101.00% | 101.00% | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Redemption date | Apr. 01, 2014 | Apr. 01, 2014 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Tender offer price for each 1000 principal amount of 2.125% notes | 1,003.27 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Unit for which the tender offer price of 2.125% notes is calculated | 1,000 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| One time debt extinguishment cost | 1,800,000 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Number of common shares under call options | 9,027,713 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Strike price of common stock shares | $ 18.29 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Amortization period of debt issuance cost | 5 years | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Senior secured credit facility | 80,000,000 | 80,000,000 | 50,000,000 | 50,000,000 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Increase in the amount of term loan or revolving credit facility | 50,000,000 | 50,000,000 | 45,000,000 | 45,000,000 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Aggregate commitment amount | 180,000,000 | 180,000,000 | 250,000,000 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Maturity of credit facility | Dec. 14, 2017 | Dec. 14, 2017 | May 14, 2013 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Variation in applicable rate for LIBOR Rate Loan | 2.50% | 2.50% | 2.75% | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Variation in applicable rate for LIBOR Rate Loan | 3.00% | 3.00% | 3.25% | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Variation in applicable rate for Base Rate Loan | 1.50% | 1.50% | 1.75% | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Variation in applicable rate for Base Rate Loan | 2.00% | 2.00% | 2.25% | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Revolving loan outstanding | 0 | 50,000,000 | 61,000,000 | 0 | 0 | 0 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Letters of credit outstanding | 3,800,000 | 4,500,000 | 2,700,000 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Term Loan | 50,000,000 | 50,000,000 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Principal payments | 2,500,000 | 2,500,000 | 6,000,000 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Base rate plus | 2.00% | 2.00% | 2.25% | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| LIBOR Plus | 3.00% | 3.00% | 3.25% | 3.21% | 3.55% | |||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Deferred acquisition costs | 5,200,000 | 5,300,000 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Redemption amount percentage of principal | 35.00% | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Redemption price | 107.50% | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Redemption price after year three | 103.75% | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Redemption price afer year five | 101.00% | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Amortization of premium | 4,000,000 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Proceeds from issuance of term note | 225,000,000 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Payments of debt extinguishment costs | 519,000 | 555,000 | 7,466,000 | 5,200,000 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Line of credit facility quarterly decrease in borrowing capacity | 2,500,000 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Line of credit facility, maximum borrowing capacity in year two | 42,500,000 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Line of credit facility, maximum borrowing capacity in year three | 37,500,000 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Long-term Debt | $ 479,205,000 | $ 653,968,000 | $ 482,723,000 | $ 300,000,000 | $ 300,000,000 | $ 129,205,000 | $ 121,723,000 | $ 50,000,000 | $ 61,000,000 | $ 50,000,000 | $ 61,000,000 | $ 225,000,000 | $ 0 | $ 125,000,000 | $ 428,968,000 | $ 429,205,000 | ||||||||||||||||||||||||||||||||||||||||||||