Consolidated Statements of Shareholders' Equity (unaudited) - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid in Capital [Member]	Retained Earnings [Member]	Treasury Stock [Member]
Beginning balance, value at Dec. 31, 2017	$ 281,247	$ 601	$ 161,809	$ 258,525	$ (139,688)
Beginning balance, shares at Dec. 31, 2017		60,149,411			2,360,838
Vesting of restricted stock		$ 3	(3)
Vesting of restricted stock, shares		297,291
Stock-based compensation	27,496		27,496
Repurchases of common stock	(16,870)				$ (16,870)
Repurchases of common stock, shares					169,146
Net income	41,160			41,160
Ending balance, value at Mar. 31, 2018	333,033	$ 604	189,302	299,685	$ (156,558)
Beginning balance, shares at Mar. 31, 2018		60,446,702			2,529,984
Beginning balance, value at Dec. 31, 2018	334,753	$ 607	203,680	395,590	$ (265,124)
Beginning balance, shares at Dec. 31, 2018		60,746,715			3,469,723
Vesting of restricted stock		$ 2	(2)
Vesting of restricted stock, shares		280,408
Stock-based compensation	36,187		36,187
Repurchases of common stock	(19,669)				$ (19,669)
Repurchases of common stock, shares					110,054
Net income	47,282			47,282
Ending balance, value at Mar. 31, 2019	$ 398,553	$ 609	$ 239,865	$ 442,872	$ (284,793)
Beginning balance, shares at Mar. 31, 2019		61,027,123			3,579,777