Shareholders' Equity - Summary of Changes in Shareholders' Equity (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended				3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2013 Common Stock [Member]	Dec. 31, 2012 Common Stock [Member]	Mar. 31, 2013 Additional Paid-In-Capital [Member]	Mar. 31, 2013 Retained Earnings [Member]	Mar. 31, 2013 Treasury Stock [Member]	Mar. 31, 2013 Deferred Compensation Trust [Member]	Mar. 31, 2013 Deferred Compensation Liability [Member]
Schedule Of 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	35,041	20,123				35,041
Deferred compensation activity								7,467	(7,467)
Equity-based compensation	8,063				8,063
Tax benefit from equity benefit plan activity	23,099				23,099
Proceeds from stock options exercised	5,412	6,003			5,412
Treasury stock issued upon option exercise and restricted share vesting					(21,312)		21,312
Balance, March 31, 2013	$ 1,552,092		$ 206	$ 206	$ 1,184,961	$ 4,374,121	$ (4,007,196)	$ (17,864)	$ 17,864