Consolidated Statements of Shareholders' Equity (USD $) In Thousands, except Share data	Total	Common stock [Member]	Additional paid-in capital [Member]	Retained earnings [Member]	Accumulated other comprehensive income (loss) [Member]
Balance at Dec. 31, 2010	$ 3,209,685	$ 1,410	$ 1,141,749	$ 2,069,496	$ (2,970)
Balance (in shares) at Dec. 31, 2010		141,026,000
Net income	507,673			507,673
Reclassification adjustment for unrealized losses on cash flow hedge, net of tax of $1,875, included in net income	2,970				2,970
Issuance of common stock under employee benefit plans, net of forfeitures and shares withheld to cover taxes	9,039	2	9,037
Issuance of common stock under employee benefit plans, net of forfeitures and shares withheld to cover taxes, shares		170,000
Net issuance of common stock upon exercise of stock options	50,309	19	50,290
Net issuance of common stock upon exercise of stock options, shares		1,861,000
Excess tax benefit of stock options exercised	22,885		22,885
Share based compensation	18,922		18,922
Share repurchases, including fees	(976,632)	(159)	(132,778)	(843,695)
Share repurchases, including fees, shares		(15,877,000)
Balance at Dec. 31, 2011	2,844,851	1,272	1,110,105	1,733,474
Balance (in shares) at Dec. 31, 2011		127,180,000
Net income	585,746			585,746
Reclassification adjustment for unrealized losses on cash flow hedge, net of tax of $1,875, included in net income	0
Issuance of common stock under employee benefit plans, net of forfeitures and shares withheld to cover taxes	9,553	1	9,552
Issuance of common stock under employee benefit plans, net of forfeitures and shares withheld to cover taxes, shares		124,000
Net issuance of common stock upon exercise of stock options	54,876	19	54,857
Net issuance of common stock upon exercise of stock options, shares		1,860,000
Excess tax benefit of stock options exercised	38,572		38,572
Share based compensation	19,996		19,996
Share repurchases, including fees	(1,445,287)	(162)	(149,172)	(1,295,953)
Share repurchases, including fees, shares	(16,201,000)	(16,201,000)
Balance at Dec. 31, 2012	2,108,307	1,130	1,083,910	1,023,267
Balance (in shares) at Dec. 31, 2012	112,963,413	112,963,000
Net income	670,292			670,292
Reclassification adjustment for unrealized losses on cash flow hedge, net of tax of $1,875, included in net income	0
Issuance of common stock under employee benefit plans, net of forfeitures and shares withheld to cover taxes	10,663		10,663
Issuance of common stock under employee benefit plans, net of forfeitures and shares withheld to cover taxes, shares		113,000
Net issuance of common stock upon exercise of stock options	59,745	14	59,731
Net issuance of common stock upon exercise of stock options, shares		1,393,000
Excess tax benefit of stock options exercised	30,811		30,811
Share based compensation	19,531		19,531
Share repurchases, including fees	(933,028)	(85)	(85,717)	(847,226)
Share repurchases, including fees, shares	(8,529,000)	(8,529,000)
Balance at Dec. 31, 2013	$ 1,966,321	$ 1,059	$ 1,118,929	$ 846,333
Balance (in shares) at Dec. 31, 2013	105,939,766	105,940,000