Income (Loss) Per Share - Commutation of Basic and Diluted Loss per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Earnings Per Share [Abstract]
Net income (loss)	$ 35,439	$ (83,891)	$ 28,169	$ 61,092	$ 13,886	$ (5,822)	$ 16,178	$ 15,185	$ 40,809	$ 39,427	$ 72,621
Undistributed income allocated to participating securities									438	556	878
Net income attributable to common stockholders									40,371	38,871	71,743
Plus: Net income effect of convertible securities									0	0	0
Numerator for diluted income per common share									$ 40,371	$ 38,871	$ 71,743
Basic weighted-average common stock shares outstanding (in shares)									50,352	45,726	45,543
Add dilutive effects of common stock equivalents (in shares)									118	29	40
Diluted weighted-average common stock shares outstanding (in shares)									50,470	45,755	45,583
Basic (USD per share)	$ 0.68	$ (1.65)	$ 0.56	$ 1.23	$ 0.30	$ (0.13)	$ 0.35	$ 0.33	$ 0.80	$ 0.85	$ 1.58
Diluted (USD per share)	$ 0.68	$ (1.65)	$ 0.56	$ 1.14	$ 0.30	$ (0.13)	$ 0.35	$ 0.33	$ 0.80	$ 0.85	$ 1.57