Earnings Per Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended												12 Months Ended
	Dec. 31, 2012		Sep. 30, 2012		Jun. 30, 2012		Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011		Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Basic:
Net Income	$ 306,480	[1]	$ 365,937	[1]	$ 96,218	[1]	$ 7,829	$ 370,577	$ 300,795	$ 80,529	[1]	$ 16,607	$ 776,464	$ 768,508	$ 684,863
Less net income allocable to participating RSUs													(7,730)	(8,821)	(7,912)
Net income available for basic common shares													768,734	759,687	676,951
Weighted average common shares outstanding	343,624		342,595		341,256		339,144	339,386	343,191	347,133		349,072	341,665	344,669	360,615
Basic net income per common share	$ 0.88		$ 1.06		$ 0.28		$ 0.02	$ 1.08	$ 0.87	$ 0.23		$ 0.05	$ 2.25	$ 2.20	$ 1.88
Diluted:
Net Income	306,480	[1]	365,937	[1]	96,218	[1]	7,829	370,577	300,795	80,529	[1]	16,607	776,464	768,508	684,863
Less net income allocable to participating RSUs													(7,682)	(8,765)	(7,863)
Net income available for diluted common shares													$ 768,782	$ 759,743	$ 677,000
Weighted average common shares outstanding	343,624		342,595		341,256		339,144	339,386	343,191	347,133		349,072	341,665	344,669	360,615
Weighted average common equivalent shares arising from:
Dilutive stock options and non-participating RSUs													4,493	3,755	3,955
Weighted average number of common and potential common shares	348,351		347,122		345,554		343,660	343,492	346,792	350,944		352,707	346,158	348,424	364,570
Diluted net income per common share	$ 0.87		$ 1.04		$ 0.28		$ 0.02	$ 1.07	$ 0.86	$ 0.23		$ 0.05	$ 2.22	$ 2.18	$ 1.86

[1] Net income for the second and third quarter of 2012 included net tax benefits of $10.5 million and $5.5 million, respectively, primarily related to reassessments of prior years' tax liabilities based on the status of current audits and tax filings in various jurisdictions, settlements, and enacted tax law changes. Net income for the fourth quarter of 2012 included the impact of the Litigation Charge, net of tax, of $87.1 million. Net income for the second quarter of 2011 included net tax benefits of $6.4 million, primarily related to reassessments of prior years' tax liabilities based on the status of audits and tax filings in various jurisdictions, settlements, and enacted tax law changes.