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								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Numerator:
Net income (loss)	$ 8,388	$ 7,832	$ 7,631	$ 5,502	$ 5,003	$ 727	$ 2,266	$ 2,038	$ 29,353	$ 10,034	$ (8,143)
Less: Net income allocated to participating securities									(260)	(286)	0
Numerator for basic and diluted earnings (loss) available to common stockholders									$ 29,093	$ 9,748	$ (8,143)
Denominator:
Weighted-average basic common shares outstanding (in shares)	60,875	57,595	57,478	48,101	47,660	39,125	31,278	31,257	56,030	37,380	22,788
Weighted-average diluted common shares outstanding (in shares)	60,875	57,595	57,478	48,101	47,660	39,125	31,278	31,257	56,030	37,380	22,788
Earnings (loss) per common share, basic (in usd per share)	$ 0.14	$ 0.13	$ 0.13	$ 0.11	$ 0.10	$ 0.02	$ 0.07	$ 0.06	$ 0.52	$ 0.26	$ (0.36)
Earnings (loss) per common share, diluted (in usd per share)	$ 0.14	$ 0.13	$ 0.13	$ 0.11	$ 0.10	$ 0.02	$ 0.07	$ 0.06	$ 0.52	$ 0.26	$ (0.36)