Shareholders' Equity - Summary of Changes in Shareholders' Equity (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended				9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013 Common Stock [Member]	Dec. 31, 2012 Common Stock [Member]	Sep. 30, 2013 Additional Paid-In-Capital [Member]	Sep. 30, 2013 Retained Earnings [Member]	Sep. 30, 2013 Treasury Stock [Member]	Sep. 30, 2013 Deferred Compensation Trust [Member]	Sep. 30, 2013 Deferred Compensation Liability [Member]
Stockholders' Equity [Line Items]
Balance, December 31, 2012			$ 1,480,477		$ 206	$ 206	$ 1,169,699	$ 4,339,080	$ (4,028,508)	$ (25,331)	$ 25,331
Net income	82,935	53,000	168,666	119,961				168,666
Deferred compensation activity										7,590	(7,590)
Purchases of common stock for treasury			(435,809)						(435,809)
Equity-based compensation			30,385				30,385
Tax benefit from equity benefit plan activity			23,811				23,811
Proceeds from stock options exercised			7,564	48,853			7,564
Treasury stock issued upon option exercise and restricted share vesting							(22,806)		22,806
Balance, September 30, 2013	$ 1,275,094		$ 1,275,094		$ 206	$ 206	$ 1,208,653	$ 4,507,746	$ (4,441,511)	$ (17,741)	$ 17,741