Earnings Per Common Share - Reconciliation of Weighted-Average Common Shares Outstanding Used in Calculation of Basic EPS to Diluted EPS (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Numerator:
Net income	$ 14,607	$ 10,281	$ 25,874
Less: Net income allocated to participating securities	(126)	(102)
Numerator for basic and diluted earnings available to common stockholders	$ 14,481	$ 10,179
Denominator:
Weighted-average basic common shares outstanding (in shares)	75,504	66,951
Weighted-average diluted common shares outstanding (in shares)	75,504	66,951
Earnings per common share, basic (in usd per share)	$ 0.19	$ 0.15
Earnings per common share, diluted (in usd per share)	$ 0.19	$ 0.15