Consolidated Statements Of Changes In Stockholders' Equity (USD $) In Thousands, except Share data	Total	Common Stock [Member]	Common Stock, Held In Treasury, At Cost [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Benefits Liability Net Of Tax [Member]	Cumulative Foreign Currency Exchange [Member]	Net Unrealized Holding Gains On Investments, Net Of Tax [Member]
Balances at Dec. 31, 2010	$ 1,505,070	$ 663		$ 452,703	$ 1,058,737	$ (12,328)	$ 5,295	$ 0
Balances, shares at Dec. 31, 2010		66,256,144
Net income	258,966				258,966
Other comprehensive (loss) income	(2,037)					(2,815)	(407)	1,185
Common stock repurchased	(2,518)		(2,518)
Common stock repurchased, shares			69,816
Stock options exercised	5,344	3		5,341
Stock options exercised, shares		274,872
Stock-based compensation, net of tax on stock options exercised	9,752	0		9,752
Stock-based compensation, net of tax on stock options exercised, shares		70,893
Dividends paid	(18,265)				(18,265)
Balances at Dec. 31, 2011	1,756,312	666	(2,518)	467,796	1,299,438	(15,143)	4,888	1,185
Balances, shares at Dec. 31, 2011		66,601,909
Common stock, held in treasury at Dec. 31, 2011			69,816
Net income	385,555				385,555
Other comprehensive (loss) income	(1,770)					(1,208)	623	(1,185)
Common stock repurchased	(10,784)		(10,784)
Common stock repurchased, shares			214,677
Stock options exercised	10,369	5		10,364
Stock options exercised, shares		522,425
Stock-based compensation, net of tax on stock options exercised	18,095	1		18,094
Stock-based compensation, net of tax on stock options exercised, shares		62,890
Dividends paid	(285,521)				(285,521)
Balances at Dec. 31, 2012	1,872,256	672	(13,302)	496,254	1,399,472	(16,351)	5,511	0
Balances, shares at Dec. 31, 2012		67,187,224
Common stock, held in treasury at Dec. 31, 2012	284,493		284,493
Net income	610,425				610,425
Other comprehensive (loss) income	8,224					9,655	(1,607)	176
Common stock repurchased	(32,918)		(32,918)
Common stock repurchased, shares			341,968
Stock options exercised	3,437	1		3,436
Stock options exercised, shares	112,962	112,962
Stock-based compensation, net of tax on stock options exercised	12,415	0		12,415
Stock-based compensation, net of tax on stock options exercised, shares		(10,082)
Dividends paid	(55,236)				(55,236)
Balances at Dec. 31, 2013	$ 2,418,603	$ 673	$ (46,220)	$ 512,105	$ 1,954,661	$ (6,696)	$ 3,904	$ 176
Balances, shares at Dec. 31, 2013		67,290,104
Common stock, held in treasury at Dec. 31, 2013	626,461		626,461