Valuation and Qualifying Accounts (Detail) (Allowance for Doubtful Accounts, USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Allowance for Doubtful Accounts
Valuation And Qualifying Accounts Disclosure [Line Items]
Balance at the beginning of the year	$ 200	$ 202	$ 36
Charged to costs and expenses	689	56	237
Write-offs	(99)	(58)	(71)
Balance at the end of the year	$ 790	$ 200	$ 202