Earnings Per Share - Components of Basic and Diluted EPS (Details) - USD ($) $ / shares in Units, $ 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	$ 7,928	$ (7,652)	$ 10,733	$ 10,515	$ 320	$ 15,103	$ 9,865	$ 3,963	$ 21,524	$ 29,251	$ 10,154
Less: income allocated to participating securities									(3)	(13)	(12)
Net income attributable to common stockholders									$ 21,521	$ 29,238	$ 10,142
Weighted average common shares outstanding — basic (in shares)									47,633,739	46,682,141	45,716,757
Dilutive effect of stock options, restricted stock units and restricted stock awards (in shares)									2,058,445	2,471,807	2,158,765
Weighted average common shares outstanding — diluted (in shares)									49,692,184	49,153,948	47,875,522
Net income per share:
Basic (USD per share)	$ 0.16	$ (0.16)	$ 0.23	$ 0.22	$ 0.01	$ 0.32	$ 0.21	$ 0.09	$ 0.45	$ 0.63	$ 0.22
Diluted (USD per share)	$ 0.16	$ (0.16)	$ 0.22	$ 0.21	$ 0.01	$ 0.31	$ 0.20	$ 0.08	$ 0.43	$ 0.59	$ 0.21