Summary of Significant Accounting Policies - Allowance for Doubtful Accounts (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Allowance for Doubtful Accounts Receivable [Roll Forward]
Beginning balance	$ 559	$ 740	$ 218
Charges to expense and deferred revenue	1,529	599	672
Write-offs	(918)	(780)	(150)
Ending balance	$ 1,170	$ 559	$ 740