Consolidated Statement of Shareholders' Equity Statement - USD ($) $ in Thousands	Total	Common Stock [Member]	Paid-in Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income [Member]
Balances at Dec. 31, 2016	$ 499,720	$ 460	$ 817,580	$ (293,920)	$ (24,400)
Net income	30,960			30,960
Other comprehensive income (loss)	7,070				7,070
Shares surrendered upon exercise and vesting of equity awards to cover taxes	(510)		(510)
Non-cash compensation expense	6,780		6,780
Balances at Dec. 31, 2017	544,020	460	823,850	(262,960)	(17,330)
Net income	83,300			83,300
Other comprehensive income (loss)	480				480
Purchase of common stock	(12,140)		(12,140)
Shares surrendered upon exercise and vesting of equity awards to cover taxes	(2,380)		(2,380)
Non-cash compensation expense	7,170		7,170
Balances at Dec. 31, 2018	620,450	460	816,500	(179,660)	(16,850)
Net income	98,620			98,620
Other comprehensive income (loss)	12,120				12,120
Purchase of common stock	(36,740)	(10)	(36,730)
Shares surrendered upon exercise and vesting of equity awards to cover taxes	(3,340)		(3,340)
Non-cash compensation expense	6,450		6,450
Impact of accounting standards adoption	(80)			1,190	(1,270)
Balances at Dec. 31, 2019	$ 697,480	$ 450	$ 782,880	$ (79,850)	$ (6,000)