Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Retained Earnings	Treasury Stock	Deferred Compensation Trust	Deferred Compensation Liability
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative-effect adjustment from adoption of ASU 2016-09, net of tax	$ 609		$ 1,566	$ (957)
Beginning Balance at Dec. 31, 2016	1,304,441	$ 206	1,515,828	5,695,376	$ (5,906,969)	$ (17,375)	$ 17,375
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	537,521			537,521
Deferred compensation activity, net						(8)	8
Purchase of common stock for treasury	(422,166)				(422,166)
Equity-based compensation	44,562		44,562
Proceeds from stock options exercised	140,525		140,525
Treasury stock issued upon option exercise and restricted share vesting			(58,284)		58,284
Ending Balance at Dec. 31, 2017	1,605,492	206	1,644,197	6,231,940	(6,270,851)	(17,383)	17,383
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative-effect adjustment from adoption of ASU 2016-09, net of tax	2,196		0	2,196
Net income	797,197			797,197
Deferred compensation activity, net						446	(446)
Purchase of common stock for treasury	(846,134)				(846,134)
Equity-based compensation	75,701		75,701
Proceeds from stock options exercised	174,110		174,110
Treasury stock issued upon option exercise and restricted share vesting			(73,785)		73,785
Ending Balance at Dec. 31, 2018	1,808,562	206	1,820,223	7,031,333	(7,043,200)	(16,937)	16,937
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	878,539			878,539
Deferred compensation activity, net						25	(25)
Purchase of common stock for treasury	(698,417)				(698,417)
Equity-based compensation	78,532		78,532
Proceeds from stock options exercised	274,028		274,028
Treasury stock issued upon option exercise and restricted share vesting			(117,376)		117,376
Ending Balance at Dec. 31, 2019	$ 2,341,244	$ 206	$ 2,055,407	$ 7,909,872	$ (7,624,241)	$ (16,912)	$ 16,912