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					$ (24,400)
Net income	$ 21,840
Other comprehensive income	4,040				4,040
Shares surrendered upon exercise and vesting of equity awards to cover taxes	(480)
Balances at Jun. 30, 2017					(20,360)
Balances at Dec. 31, 2017	544,020	$ 460	$ 823,850	$ (262,960)	(17,330)
Net income	43,920			43,920
Other comprehensive income	430				430
Purchase of common stock	(2,920)		(2,920)
Shares surrendered upon exercise and vesting of equity awards to cover taxes	(2,380)		(2,380)
Non-cash compensation expense	2,620		2,620
Balances at Jun. 30, 2018	$ 585,690	$ 460	$ 821,170	$ (219,040)	$ (16,900)