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, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014 Common Stock [Member]	Dec. 31, 2013 Common Stock [Member]	Jun. 30, 2014 Additional Paid-In-Capital [Member]	Jun. 30, 2014 Retained Earnings [Member]	Jun. 30, 2014 Treasury Stock [Member]	Jun. 30, 2014 Deferred Compensation Trust [Member]	Dec. 31, 2013 Deferred Compensation Trust [Member]	Jun. 30, 2014 Deferred Compensation Liability [Member]	Dec. 31, 2013 Deferred Compensation Liability [Member]
Stockholders' Equity [Line Items]
Beginning Balance			$ 1,261,352		$ 206	$ 206	$ 1,212,050	$ 4,605,557	$ (4,556,461)	$ (17,741)	$ (17,741)	$ 17,741	$ 17,741
Net income	68,178	50,690	92,027	85,731				92,027
Purchase of common stock for treasury			(347,448)						(347,448)
Equity-based compensation			26,641				26,641
Tax benefit from equity benefit plan activity			6,050				6,050
Proceeds from stock options exercised			60,593	6,671			60,593
Treasury stock issued upon option exercise and restricted share vesting			0				(27,579)		27,579
Ending Balance	$ 1,099,215		$ 1,099,215		$ 206	$ 206	$ 1,277,755	$ 4,697,584	$ (4,876,330)	$ (17,741)	$ (17,741)	$ 17,741	$ 17,741