Consolidated Statements of Changes in Stockholders' Equity (USD $) In Thousands, except Share data	Total	Common Stock ($.001 Par Value)	Paid-In Capital in Excess of Par	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock (at cost)
Beginning balance at Dec. 31, 2011	$ 4,806,498	$ 403	$ 3,090,374	$ 1,909,475	$ (418)	$ (193,336)
Beginning balance, shares at Dec. 31, 2011		402,946,070				13,965,673
Repurchase of common stock, value	(266,657)					(266,657)
Repurchase of common stock, shares	16,978,000					16,978,008
Issued or purchased pursuant to employee stock compensation plans, value	6,024	3	6,021
Issued or purchased pursuant to employee stock compensation plans, shares		3,197,476
Issued pursuant to employee stock purchase plan, value	13,260		1,607			11,653
Issued pursuant to employee stock purchase plan, shares						(815,385)
Issued pursuant to directors' compensation plan, value	321		321
Issued pursuant to directors' compensation plan, shares		19,648
Stock-based compensation	37,897		37,897
Income tax benefit from equity awards	241		241
Tax withholding - stock compensation, value	(8,125)					(8,125)
Tax withholding - stock compensation, shares						472,966
Derivative contracts, net	70				70
Net income	525,360			525,360
Ending balance at Dec. 31, 2012	5,114,889	406	3,136,461	2,434,835	(348)	(456,465)
Ending balance, shares at Dec. 31, 2012		406,163,194				30,601,262
Repurchase of common stock, value	(277,768)					(277,768)
Repurchase of common stock, shares	16,469,000					16,468,648
Issued or purchased pursuant to employee stock compensation plans, value	5,489	3	5,486
Issued or purchased pursuant to employee stock compensation plans, shares		3,038,767
Issued pursuant to employee stock purchase plan, value	15,104		1,844			13,260
Issued pursuant to employee stock purchase plan, shares						(860,901)
Issued pursuant to directors' compensation plan, value	344		344
Issued pursuant to directors' compensation plan, shares		13,612
Stock-based compensation	42,091		42,091
Income tax benefit from equity awards	488		488
Tax withholding - stock compensation, value	(8,900)					(8,900)
Tax withholding - stock compensation, shares						501,887
Derivative contracts, net	72				72
Net income	409,597			409,597
Ending balance at Dec. 31, 2013	5,301,406	409	3,186,714	2,844,432	(276)	(729,873)
Ending balance, shares at Dec. 31, 2013		409,215,573				46,710,896
Repurchase of common stock, value	(200,369)					(200,369)
Repurchase of common stock, shares	12,398,000					12,398,017
Issued or purchased pursuant to employee stock compensation plans, value	7,023	3	7,020
Issued or purchased pursuant to employee stock compensation plans, shares		2,541,809
Issued pursuant to employee stock purchase plan, value	16,358		(3,272)			19,630
Issued pursuant to employee stock purchase plan, shares						(1,247,156)
Issued pursuant to directors' compensation plan, value	412		412
Issued pursuant to directors' compensation plan, shares		22,529
Stock-based compensation	39,532		39,532
Income tax benefit from equity awards	12		12
Tax withholding - stock compensation, value	(8,618)					(8,618)
Tax withholding - stock compensation, shares						553,750
Derivative contracts, net	67				67
Cash dividends declared ($0.25 per common share)	(87,458)			(87,458)
Net income	635,491			635,491
Ending balance at Dec. 31, 2014	$ 5,703,856	$ 412	$ 3,230,418	$ 3,392,465	$ (209)	$ (919,230)
Ending balance, shares at Dec. 31, 2014		411,779,911				58,415,507