Shareholders' Equity (Details) (USD $) In Thousands, except Share data	3 Months Ended		9 Months Ended				9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011 Common Stock [Member]	Dec. 31, 2010 Common Stock [Member]	Sep. 30, 2011 Additional Paid-in Capital [Member]	Sep. 30, 2011 Retained Earnings [Member]	Sep. 30, 2011 Treasury Stock [Member]	Sep. 30, 2011 Deferred Compensation Trust [Member]	Sep. 30, 2011 Deferred Compensation Liability [Member]
Summary of changes in shareholders' equity
Balance, December 31, 2010			$ 1,740,374		$ 206	$ 206	$ 951,234	$ 4,029,072	$ (3,240,138)	$ (27,582)	$ 27,582
Net income	43,409	43,944	97,028	147,307				97,028
Deferred compensation activity										2,000	(2,000)
Purchase of common stock for treasury			(666,628)						(666,628)
Equity-based compensation			47,966				47,966
Tax benefit from stock options exercised and deferred compensation distributions			21,272				21,272
Proceeds from stock options exercised			106,007	56,993			106,007
Treasury stock issued upon option exercise							(72,245)		72,245
Balance, September 30, 2011	1,346,019		1,346,019		206	206	1,054,234	4,126,100	(3,834,521)	(25,582)	25,582
Shareholders' Equity (Textuals) [Abstract]
Common stock repurchased			979,265
Aggregate purchase price of common stock			$ 666,628						$ 666,628
Stock option exercised			331,000