Summary of Significant Accounting Policies - Activity of Allowance for Doubtful Accounts (Detail) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Allowance for Doubtful Accounts Receivable [Roll Forward]
Beginning balance	$ 140	$ 50
Charges to costs and expenses	155	105
Accounts charged off, less recoveries	14	(15)
Ending balance	$ 309	$ 140