Earnings Per Common Share - Reconciliation of Weighted-Average Common Shares Outstanding Used in Calculation of Basic EPS to Diluted EPS (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Numerator:
Net income	$ 2,030	$ 7,631	$ 12,311	$ 13,133	$ 29,353
Less: Net income allocated to participating securities	(91)	(69)	(193)	(147)
Numerator for basic and diluted earnings available to common stockholders	$ 1,939	$ 7,562	$ 12,118	$ 12,986
Denominator:
Weighted-average basic common shares outstanding (in shares)	72,564	57,478	69,773	52,789
Weighted-average diluted common shares outstanding (in shares)	72,564	57,478	69,773	52,789
Earnings per common share, basic (in usd per share)	$ 0.03	$ 0.13	$ 0.17	$ 0.25
Earnings per common share, diluted (in usd per share)	$ 0.03	$ 0.13	$ 0.17	$ 0.25