Registration of securities issued in business combination transactions

Income Tax Benefit/Expense - Additional Information (Detail)

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Income Tax Benefit/Expense - Additional Information (Detail) (USD $)
 3 Months Ended 9 Months Ended 12 Months Ended
Sep. 30, 2013
Sep. 30, 2012
Sep. 30, 2013
Sep. 30, 2012
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Income Tax Disclosure [Line Items]              
Income tax benefit $ 9,112,000 $ 6,695,000 $ 18,841,000 $ 31,155,000 $ 33,879,000 $ (14,767,000) $ 26,213,000
Depreciation and amortization 35,882,000 29,779,000 97,674,000 85,357,000 113,017,000 112,136,000 115,030,000
Decrease in valuation allowance         1,700,000    
Non-cash pretax impairment charge relating to AADU rigs in Alaska           170,000,000  
Increased valuation allowance           2,500,000  
Increase in tax expense             14,500,000
Net of anticipated tax benefits             6,800,000
Approximated tax amount             6,500,000
Approximated interest amount             4,800,000
Approximated amount of penalties             3,200,000
Increase in tax expense from subsidiary settlement             1,200,000
Tax             600,000
Interest             100,000
Penalties             500,000
Liability for unrecognized tax benefits 10,500,000 12,000,000 10,500,000 12,000,000 (10,030,000) (15,492,000)  
Unrecognized tax benefits 3,800,000 5,200,000 3,800,000 5,200,000 3,200,000    
Accrued interest and penalties related to uncertain tax positions         7,000,000 8,400,000  
Increase of interest         200,000    
Increase of penalties         1,100,000    
Proceeds from income tax refunds     22,400,000        
Interest from income tax refunds     2,200,000        
Rig [Member]
              
Income Tax Disclosure [Line Items]              
Depreciation and amortization         7,700,000    
Us Federal Internal Revenue Service Examination [Member]
              
Income Tax Disclosure [Line Items]              
Income tax benefit         1,700,000    
Federal And State Jurisdiction [Member]
              
Income Tax Disclosure [Line Items]              
Income tax benefit           $ 60,900,000