Statements of Shareholders’ Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Treasury Stock	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Restatement Adjustment Retained Earnings
Balance at Dec. 31, 2016	$ 1,385,184	$ 7	$ 551,004	$ (218,692)	$ 1,054,210	$ (1,345)
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
Retirement of treasury stock	0		(199,418)	199,418
Changes in comprehensive income	(119)					(119)
Net income	415,522				415,522
Balance at Dec. 31, 2017	1,762,574	7	360,153	(65,854)	1,469,732	(1,464)
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
Retirement of treasury stock			0
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)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation	8,154		8,154
Repurchase of common stock	(5,439)			(5,439)
Proceeds from options exercised	1		1
Retirement of treasury stock			0
Changes in comprehensive income	406					406
Net income	335,255				335,255
Balance at Dec. 31, 2019	$ 2,261,332	$ 7	$ 379,380	$ (72,455)	$ 1,955,187	$ (787)
Balance (Accounting Standards Update 2016-02) at Dec. 31, 2019							$ (5,549)