Net (Loss) Income Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Earnings Per Share [Abstract]
Net income (loss)	$ 26,981	$ 23,587	$ 12,713	$ 17,073	$ 69,900	$ (450,352)	$ 22,107	$ 15,595	$ 80,354	$ (342,750)	$ 101,002
Less: net (income) loss allocated to unvested participating restricted stock									(2,711)	6,768	(1,430)
Net income (loss) available to common stockholders									77,643	(335,982)	99,572
Effect of unvested participating restricted stock									16	0	2
Numerator - net income (loss) available to common shareholders - diluted									$ 77,659	$ (335,982)	$ 99,574
Weighted average outstanding shares of common stock - basic (shares)									17,533	17,725	18,030
Stock options (shares)									256	15	95
Weighted average outstanding shares of common stock - diluted (shares)									17,789	17,740	18,125
Basic (USD per share)	$ 1.49	$ 1.31	$ 0.70	$ 0.93	$ 3.82	$ (24.91)	$ 1.23	$ 0.87	$ 4.43	$ (18.96)	$ 5.52
Diluted (USD per share)	$ 1.47	$ 1.29	$ 0.69	$ 0.92	$ 3.82	$ (24.91)	$ 1.23	$ 0.86	$ 4.37	$ (18.96)	$ 5.49