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, 2009	$ 1,284,982	$ 660		$ 442,469	$ 853,358	$ (15,856)	$ 4,351	$ 0
Balances, shares at Dec. 31, 2009		65,979,951
Net income	221,393				221,393
Other comprehensive (loss) income	4,472					3,528	944	0
Stock options exercised	3,747	2		3,745
Stock options exercised, shares		173,014
Stock-based compensation, net of tax on stock options exercised	6,490	1		6,489
Stock-based compensation, net of tax on stock options exercised, shares		103,179
Dividends paid	(16,014)				(16,014)
Balances at Dec. 31, 2010	1,505,070	663	0	452,703	1,058,737	(12,328)	5,295	0
Balances, shares at Dec. 31, 2010		66,256,144
Common stock, held in treasury at Dec. 31, 2010			0
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		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	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