Error Corrections and Prior Period Adjustment Restatement (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2011
Assets
Current deferred income taxes	$ 45,353	$ 43,032	$ 48,743
Prepaid expenses	26,384	21,598	27,809
Total current assets	1,049,255	863,100	1,003,711
Total assets	8,225,916	8,229,314	8,383,526
Liabilities
Other current liabilities	213,735	167,560	239,438
Total current liabilities	632,097	406,253	380,980
Noncurrent deferred income taxes	680,880	732,528	794,921
Total liabilities	4,458,719	4,437,697	4,516,609
Equity
Retained earnings	1,274,465	1,334,476	1,363,640
Total equity	3,767,197	3,791,617	3,866,917
Total liabilities and equity	8,225,916	8,229,314	8,383,526
As Reported [Member]
Assets
Current deferred income taxes			47,833
Prepaid expenses			27,074
Total current assets			1,002,066
Total assets			8,381,881
Liabilities
Other current liabilities			222,762
Total current liabilities			364,304
Noncurrent deferred income taxes			800,770
Total liabilities			4,505,782
Equity
Retained earnings			1,372,822
Total equity			3,876,099
Total liabilities and equity			8,381,881
Correction [Member]
Assets
Current deferred income taxes			910
Prepaid expenses			735
Total current assets			1,645
Total assets			1,645
Liabilities
Other current liabilities			16,676
Total current liabilities			16,676
Noncurrent deferred income taxes			(5,849)
Total liabilities			10,827
Equity
Retained earnings			(9,182)
Total equity			(9,182)
Total liabilities and equity			$ 1,645