Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid in Capital [Member]	Retained Earnings [Member]	Treasury Stock [Member]
Beginning balance, value at Dec. 31, 2016	$ 205,693	$ 585	$ 120,027	$ 135,039	$ (49,958)
Beginning balance, shares at Dec. 31, 2016		58,453,000			1,122,000
Vesting of restricted stock		$ 16	(16)
Vesting of restricted stock, shares		1,696,000
Stock-based compensation	41,798		41,798
Repurchases of common stock	(89,730)				$ (89,730)
Repurchases of common stock, shares					1,239,000
Net income	123,486			123,486
Ending balance, value at Dec. 31, 2017	281,247	$ 601	161,809	258,525	$ (139,688)
Ending balance, shares at Dec. 31, 2017		60,149,000			2,361,000
Vesting of restricted stock		$ 6	(6)
Vesting of restricted stock, shares		598,000
Stock-based compensation	41,877		41,877
Repurchases of common stock	(125,436)				$ (125,436)
Repurchases of common stock, shares					1,109,000
Net income	137,065			137,065
Ending balance, value at Dec. 31, 2018	334,753	$ 607	203,680	395,590	$ (265,124)
Ending balance, shares at Dec. 31, 2018		60,747,000			3,470,000
Vesting of restricted stock		$ 6	(6)
Vesting of restricted stock, shares		603,000
Stock-based compensation	53,827		53,827
Repurchases of common stock	(42,528)				$ (42,528)
Repurchases of common stock, shares					219,000
Net income	180,576			180,576
Ending balance, value at Dec. 31, 2019	$ 526,628	$ 613	$ 257,501	$ 576,166	$ (307,652)
Ending balance, shares at Dec. 31, 2019		61,350,000			3,689,000