Annual report pursuant to Section 13 and 15(d)

Income Taxes - Additional Information (Detail)

v2.4.0.6
Income Taxes - Additional Information (Detail) (USD $)
 12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Income Tax Disclosure [Line Items]      
Income tax benefit $ 33,879,000 $ (14,767,000) $ 26,213,000
Depreciation and amortization 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 (10,030,000) (15,492,000)  
Unrecognized tax benefits 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    
Rig [Member]
      
Income Tax Disclosure [Line Items]      
Depreciation and amortization 7,700,000    
Federal And State Jurisdiction [Member]
      
Income Tax Disclosure [Line Items]      
Income tax benefit   60,900,000  
Us Federal Internal Revenue Service Examination [Member]
      
Income Tax Disclosure [Line Items]      
Income tax benefit $ 1,700,000