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Tax Effect Of Significant Temporary Differences Representing Deferred Tax Assets And Liabilities (Detail) (USD $)
In Thousands, unless otherwise specified
 12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Schedule of Deferred Income Tax Assets and Liabilities [Line Items]      
Ending Balance $ 64,443 $ 157,380 $ 41,944
Net Change (92,937) 115,436 (2,296)
Beginning Balance 157,380 41,944 44,240
Ending Balance 63,580 62,092 46,903
Net Change 1,488 15,189 4,485
Beginning Balance 62,092 46,903 42,418
Deferred Tax Ending Balance 128,023 219,472 88,847
Net Change (91,449) 130,625 2,189
Beginning Balance 219,472 88,847 86,658
Ending Balance (920,882) (848,724) (558,325)
Net Change (72,158) (290,399) (134,251)
Beginning Balance (848,724) (558,325) (424,074)
Ending Balance (932,366) (863,379) (573,454)
Net Change (68,987) (289,925) (138,017)
Beginning Balance (863,379) (573,454) (435,437)
Ending Balance (804,343) (643,907) (484,607)
Net Change (160,436) (159,300) (135,828)
Beginning Balance (643,907) (484,607) (348,779)
Net Operating Loss Carryforwards
      
Schedule of Deferred Income Tax Assets and Liabilities [Line Items]      
Ending Balance 18,914 114,576  
Net Change (95,662) 114,576  
Beginning Balance 114,576    
Ending Balance 11,762 18,434 6,465
Net Change (6,672) 11,969 1,593
Beginning Balance 18,434 6,465 4,872
Workers Compensation Allowance
      
Schedule of Deferred Income Tax Assets and Liabilities [Line Items]      
Ending Balance 25,078 24,004 23,290
Net Change 1,074 714 (1,334)
Beginning Balance 24,004 23,290 24,624
Other
      
Schedule of Deferred Income Tax Assets and Liabilities [Line Items]      
Ending Balance 20,451 18,800 18,654
Net Change 1,651 146 (962)
Beginning Balance 18,800 18,654 19,616
Ending Balance 15,124 10,670 16,031
Net Change 4,454 (5,361) 6,546
Beginning Balance 10,670 16,031 9,485
Ending Balance (11,484) (14,655) (15,129)
Net Change 3,171 474 (3,766)
Beginning Balance (14,655) (15,129) (11,363)
Ending Balance (15,285) (12,901) (11,670)
Net Change (2,384) (1,231) (709)
Beginning Balance (12,901) (11,670) (10,961)
Expense associated with employee stock options
      
Schedule of Deferred Income Tax Assets and Liabilities [Line Items]      
Ending Balance 14,672 12,728 11,252
Net Change 1,944 1,476 2,123
Beginning Balance 12,728 11,252 9,129
Federal benefit of foreign deferred tax liabilities
      
Schedule of Deferred Income Tax Assets and Liabilities [Line Items]      
Ending Balance       
Net Change     (9,160)
Beginning Balance     9,160
Federal benefit of state deferred tax liabilities
      
Schedule of Deferred Income Tax Assets and Liabilities [Line Items]      
Ending Balance 22,022 20,260 13,155
Net Change 1,762 7,105 3,383
Beginning Balance 20,260 13,155 9,772
Property and equipment basis difference
      
Schedule of Deferred Income Tax Assets and Liabilities [Line Items]      
Ending Balance (905,597) (835,823) (546,655)
Net Change (69,774) (289,168) (133,542)
Beginning Balance $ (835,823) $ (546,655) $ (413,113)