Quarterly Financial Data (Unaudited) - Components of Quarterly Financial Data (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Condensed Income Statements, Captions [Line Items]
Revenue	$ 39,988	$ 39,248	$ 39,935	$ 40,449	$ 42,200	$ 43,027	$ 44,732	$ 45,633	$ 159,620	$ 175,592
(Loss) income from operations	1,608	(2,256)	(5,740)	(3,691)	(419)	(1,321)	267	962	(10,079)	(511)
(Loss) income from continuing operations before income taxes	1,270	(2,960)	(7,765)	(4,250)	(1,150)	(2,176)	(668)	630	(13,705)	(3,364)
Net loss	$ 3,077	$ (3,995)	$ (8,604)	$ (4,802)	$ (12,788)	$ (8,108)	$ (5,307)	$ (4,266)	$ (14,324)	$ (30,469)
Net (loss) income per common share, basic and diluted (in dollars per share)	$ 0.13	$ (0.17)	$ (0.36)	$ (0.20)	$ (0.54)	$ (0.35)	$ (0.23)	$ (0.19)	$ (0.60)	$ (1.31)
Scenario, Previously Reported
Condensed Income Statements, Captions [Line Items]
(Loss) income from operations		$ (2,659)	$ (3,318)	$ (3,691)
(Loss) income from continuing operations before income taxes		(3,363)	(5,343)	(4,250)
Net loss		$ (4,399)	$ (6,182)	$ (4,802)
Net (loss) income per common share, basic and diluted (in dollars per share)		$ (0.18)	$ (0.26)	$ (0.20)
Restatement Adjustment
Condensed Income Statements, Captions [Line Items]
Share-based compensation expense		$ (403)	$ 2,400