Shareholders' Equity - Summary of Changes in Shareholders' Equity (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended				6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013 Common Stock [Member]	Dec. 31, 2012 Common Stock [Member]	Jun. 30, 2013 Additional Paid-In-Capital [Member]	Jun. 30, 2013 Retained Earnings [Member]	Jun. 30, 2013 Treasury Stock [Member]	Jun. 30, 2013 Deferred Compensation Trust [Member]	Jun. 30, 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	50,690	46,838	85,731	66,961				85,731
Deferred compensation activity										7,590	(7,590)
Purchase of common stock for treasury			(294,979)						(294,979)
Equity-based compensation			18,652				18,652
Tax benefit from equity benefit plan activity			23,727				23,727
Proceeds from stock options exercised			6,671	42,182			6,671
Treasury stock issued upon option exercise and restricted share vesting							(22,364)		22,364
Balance, June 30, 2013	$ 1,320,279		$ 1,320,279		$ 206	$ 206	$ 1,196,385	$ 4,424,811	$ (4,301,123)	$ (17,741)	$ 17,741