Summary of Significant Accounting Policies - Summary of Adjustments in Allowances for Doubtful Accounts and Sales Adjustments (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Accounting Policies [Abstract]
Balance at beginning of year	$ 1,113	$ 1,621	$ 990
Provisions for losses - accounts receivable	(1,897)	(729)	(961)
Deductions for accounts charged off or credits issued	(1,285)	(1,237)	(330)
Balance at end of year	$ 1,725	$ 1,113	$ 1,621