Earnings Per Common Share - Summary of Reconciliation of Earnings (Loss) Per Common Share (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
Basic Earnings (Loss) per Common Share:
Net loss	$ (5,756)	$ (5,198)	$ (5,283)	$ (5,435)	$ (5,303)	$ (4,469)	$ (4,012)	$ (4,150)	$ (21,672)	$ (17,934)	$ (15,820)
Distributed earnings to common shares											1,553
Distributed earnings to participating securities											101
Total distributed earnings											1,654
Undistributed loss allocable to common shares									(21,672)	(17,934)	(17,474)
Total undistributed loss									(21,672)	(17,934)	(17,474)
Loss to common shares—basic									$ (21,672)	$ (17,934)	$ (15,921)
Weighted average common shares outstanding—basic	10,111	9,506	8,587	8,533	8,485	8,309	8,029	7,960	9,188	8,198	7,187
Basic earnings (loss) per common share	$ (0.57)	$ (0.55)	$ (0.62)	$ (0.64)	$ (0.62)	$ (0.54)	$ (0.50)	$ (0.52)	$ (2.36)	$ (2.19)	$ (2.22)
Diluted Earnings (Loss) per Common Share:
Loss to common shares—basic									$ (21,672)	$ (17,934)	$ (15,921)
Loss to common shares—diluted									$ (21,672)	$ (17,934)	$ (15,921)
Weighted average common shares outstanding— basic	10,111	9,506	8,587	8,533	8,485	8,309	8,029	7,960	9,188	8,198	7,187
Weighted average common shares outstanding— dilutive	10,111	9,506	8,587	8,533	8,485	8,309	8,029	7,960	9,188	8,198	7,187
Diluted earnings (loss) per common share	$ (0.57)	$ (0.55)	$ (0.62)	$ (0.64)	$ (0.62)	$ (0.54)	$ (0.50)	$ (0.52)	$ (2.36)	$ (2.19)	$ (2.22)