Summary of Significant Accounting Policies - Activity of Allowance for Doubtful Accounts (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Allowance for Doubtful Accounts Receivable [Roll Forward]
Beginning balance	$ 389	$ 140
Charges to costs and expenses	(235)	235
Accounts write offs, less recoveries	(123)	14
Ending balance	$ 31	$ 389