Stock-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands					3 Months Ended		9 Months Ended		12 Months Ended
	Jun. 17, 2015	Sep. 15, 2014	Sep. 08, 2014	Mar. 31, 2014	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options, granted					203,000	10,000	254,800	114,300
Weighted-average grant date fair value					$ 8.49	$ 2.29	$ 8.10	$ 3.15
Additional expense for modifications							$ 201		$ 325
Unrecognized compensation costs, employee stock options					$ 5,100		$ 5,100
Expected recognition period							1 year 7 months 2 days
Employee Two
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares vested				33,333
Director
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares vested	157,500
Shares vesting period	48 months
Vested options held by 1 employee
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares vested		39,167	82,834	71,167
Shares vesting period				9 months
Unvested options held by 1 employee
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares vesting period		27 months	3 months	6 months
Shares unvested		113,333	23,333	66,667
Unvested Restricted Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected recognition period							1 year 9 months 29 days
Unrecognized compensation costs					$ 8,600		$ 8,600
Restricted Stock | Director
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share vesting date							Dec. 31, 2015
Restricted Stock | Employees and Directors
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares vesting period					3 years
Shares issued					4,186	0	1,054,186	0