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		9 Months Ended		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Numerator:
Net income	$ 11,311	$ 7,832	$ 23,622	$ 20,965	$ 29,353
Less: Net income allocated to participating securities	(83)	(58)	(277)	(205)
Numerator for basic and diluted earnings available to common stockholders	$ 11,228	$ 7,774	$ 23,345	$ 20,760
Denominator:
Weighted-average basic common shares outstanding (in shares)	75,471	57,595	71,693	54,403
Weighted-average diluted common shares outstanding (in shares)	75,471	57,595	71,693	54,403
Earnings per common share, basic (in usd per share)	$ 0.15	$ 0.13	$ 0.33	$ 0.38
Earnings per common share, diluted (in usd per share)	$ 0.15	$ 0.13	$ 0.33	$ 0.38