Summary of Significant Accounting Policies - Summary of Adjustments in Allowances for Doubtful Accounts and Sales Adjustments (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance at beginning of year	$ 1,640	$ 1,725	$ 1,113
Provisions for losses - accounts receivable	4,484	1,756	1,897
Collection of accounts previously written off	0	153	0
Deductions for accounts charged off or credits issued	(2,728)	(1,994)	(1,285)
Balance at end of year	$ 3,396	$ 1,640	$ 1,725