Statements of Shareholders’ Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Treasury Stock	Retained Earnings (Accumulated Deficit)	Accumulated Other Comprehensive Income (Loss)	As Reported [Member]	As Reported [Member] Additional Paid-In Capital	As Reported [Member] Treasury Stock	As Reported [Member] Retained Earnings (Accumulated Deficit)	As Reported [Member] Accumulated Other Comprehensive Income (Loss)	Restatement Adjustment [Member]	Restatement Adjustment [Member] Retained Earnings (Accumulated Deficit)
Balance at Dec. 31, 2015	$ 1,217,283	$ 7	$ 544,277	$ (116,182)	$ 790,727	$ (1,546)	$ 1,225,310	$ 544,277	$ (116,182)	$ 798,754	$ (1,546)
Balance (ASU 2014-09) at Dec. 31, 2015												$ (8,027)	$ (8,027)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation	7,105		7,105
Repurchase of common stock	(102,510)			(102,510)
Proceeds from options exercised	92		92
Excess tax benefits from share-based compensation	(470)		(470)
Changes in comprehensive income	201					201
Net income	263,483				263,483		264,879
Net income | ASU 2014-09												(1,396)
Balance at Dec. 31, 2016	1,385,184	7	551,004	(218,692)	1,054,210	(1,345)	1,394,607
Balance (ASU 2014-09) at Dec. 31, 2016												(9,423)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation	8,522		8,522
Repurchase of common stock	(46,580)			(46,580)
Proceeds from options exercised	45		45
Changes in comprehensive income	(119)					(119)
Retirement of treasury stock	0		(199,418)	199,418
Net income	415,522				415,522		420,606
Net income | ASU 2014-09												(5,084)
Balance at Dec. 31, 2017	1,762,574	7	360,153	(65,854)	1,469,732	(1,464)	$ 1,777,081
Balance (ASU 2014-09) at Dec. 31, 2017												$ (14,507)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation	11,021		11,021
Repurchase of common stock	(1,162)			(1,162)
Proceeds from options exercised	51		51
Changes in comprehensive income	271					271
Net income	155,749				155,749
Balance at Dec. 31, 2018	$ 1,928,504	$ 7	$ 371,225	$ (67,016)	$ 1,625,481	$ (1,193)