Earnings Per Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended														12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013		Jun. 30, 2013		Mar. 31, 2013		Dec. 31, 2012		Sep. 30, 2012		Jun. 30, 2012		Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Basic:
Net Income	$ 369,249	$ 422,836	[1]	$ 73,348	[1]	$ 38,511	[1]	$ 306,480	[1]	$ 365,937	[1]	$ 96,218	[1]	$ 7,829	$ 903,944	$ 776,464	$ 768,508
Less: Net income allocable to participating RSUs															(8,335)	(7,730)	(8,821)
Net income available for basic common shares															895,609	768,734	759,687
Weighted average common shares outstanding	339,402	343,279		346,614		344,315		343,624		342,595		341,256		339,144	343,394	341,665	344,669
Basic net income per common share	$ 1.08	$ 1.22		$ 0.21		$ 0.11		$ 0.88		$ 1.06		$ 0.28		$ 0.02	$ 2.61	$ 2.25	$ 2.20
Diluted:
Net Income	369,249	422,836	[1]	73,348	[1]	38,511	[1]	306,480	[1]	365,937	[1]	96,218	[1]	7,829	903,944	776,464	768,508
Less: Net income allocable to participating RSUs															(8,291)	(7,682)	(8,765)
Net income available for diluted common shares															$ 895,653	$ 768,782	$ 759,743
Weighted average common shares outstanding	339,402	343,279		346,614		344,315		343,624		342,595		341,256		339,144	343,394	341,665	344,669
Weighted average common equivalent shares arising from:
Dilutive stock options and non-participating RSUs															4,065	4,493	3,755
Weighted average number of common and potential common shares	343,237	346,695		350,424		348,795		348,351		347,122		345,554		343,660	347,459	346,158	348,424
Diluted net income per common share	$ 1.07	$ 1.21		$ 0.21		$ 0.11		$ 0.87		$ 1.04		$ 0.28		$ 0.02	$ 2.58	$ 2.22	$ 2.18

[1] Net income for the first quarter of 2013 included $4.0 million of net tax benefits primarily related to enacted tax law changes. Net income for the second and third quarter of 2013 included net tax benefits of $11.2 million and $17.0 million, respectively, 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. 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 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.