Schedule of Allowance for Doubtful Accounts (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Receivables [Abstract]
Beginning balance	$ 269	$ 345	$ 266
Charges to costs and expenses	(50)	20	133
Write-offs	(14)	(96)	(155)
Recoveries	3		101
Ending balance	$ 208	$ 269	$ 345