Unaudited Supplementary Quarterly Financial Information - Unaudited Supplementary Quarterly Financial Information (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	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Total revenue	$ 24,957		$ 27,361	$ 30,305	$ 29,130	$ 29,774		$ 30,826	$ 34,024	$ 31,898	$ 111,753	$ 126,522	$ 116,704
Gross profit	7,880		10,321	11,509	9,988	11,978		10,640	12,814	10,750	39,698	46,182	39,590
Net (loss) income	$ (25,417)	[1]	$ (172)	$ (860)	$ (2,687)	$ (3,427)	[1]	$ 43	$ 1,313	$ (763)	$ (29,136)	$ (2,834)	$ (4,060)
Basic (loss) income per share	$ (1.82)		$ (0.01)	$ (0.06)	$ (0.21)	$ (0.28)		$ 0.00	$ 0.11	$ (0.06)	$ (2.14)	$ (0.23)	$ (0.35)
Diluted (loss) income per share	$ (1.82)		$ (0.01)	$ (0.06)	$ (0.21)	$ (0.28)		$ 0.00	$ 0.09	$ (0.06)	$ (2.14)	$ (0.23)	$ (0.35)

[1] (1) The Company's fourth quarter 2017 and 2016 net loss includes $22.0 million and $3.7 million, respectively, of expense associated with the increase to the valuation allowance applied against the carrying value of its deferred tax attributes and the impairment of certain state net operating loss carryforwards.