Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2015		55,581,005
Beginning balance at Dec. 31, 2015	$ 1,152,357	$ 556	$ 1,202,418	$ (50,617)
Increase (Decrease) in Stockholders' Equity
Common shares issued under share-based compensation plans, net of shares withheld for employee taxes (in shares)		18,707
Common shares issued under share-based compensation plans, net of shares withheld for employee taxes	30	$ 0	30
Repurchased of common stock (in shares)		(1,134,528)
Repurchases of common stock	(12,522)	$ (11)	(12,511)
Dividends on common stock	(24,648)			(24,648)
Share-based compensation	74		74
Net loss	(109,186)			(109,186)
Ending balance (in shares) at Jun. 30, 2016		54,465,184
Ending balance at Jun. 30, 2016	$ 1,006,105	$ 545	1,190,011	(184,451)
Beginning balance (in shares) at Dec. 31, 2016	53,667,631	53,667,631
Beginning balance at Dec. 31, 2016	$ 863,068	$ 537	1,182,245	(319,714)
Increase (Decrease) in Stockholders' Equity
Common shares issued under share-based compensation plans, net of shares withheld for employee taxes (in shares)		49,657
Common shares issued under share-based compensation plans, net of shares withheld for employee taxes	50	$ 1	49
Repurchased of common stock (in shares)		(357,848)
Repurchases of common stock	(5,008)	$ (4)	(5,004)
Dividends on common stock	(15,940)			(15,940)
Share-based compensation	2,466		2,466
Net loss	$ (105,064)			(105,064)
Ending balance (in shares) at Jun. 30, 2017	53,359,440	53,359,440
Ending balance at Jun. 30, 2017	$ 739,572	$ 534	$ 1,179,756	$ (440,718)