Condensed Consolidated Statements of Stockholders' Equity - 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)		(1,730,070)
Repurchases of common stock	(18,784)	$ (17)	(18,767)
Dividends on common stock	(32,874)			(32,874)
Share-based compensation	493		493
Net loss	(166,824)			(166,824)
Ending balance (in shares) at Sep. 30, 2016		53,869,642
Ending balance at Sep. 30, 2016	$ 934,398	$ 539	1,184,174	(250,315)
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)		150,613
Common shares issued under share-based compensation plans, net of shares withheld for employee taxes	105	$ 1	104
Repurchased of common stock (in shares)		(370,294)
Repurchases of common stock	(5,165)	$ (4)	(5,161)
Dividends on common stock	(24,011)			(24,011)
Share-based compensation	2,824		2,824
Net loss	$ (147,980)			(147,980)
Ending balance (in shares) at Sep. 30, 2017	53,447,950	53,447,950
Ending balance at Sep. 30, 2017	$ 688,841	$ 534	$ 1,180,012	$ (491,705)