Accounts Receivable - Changes in 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]
Balance at beginning of year	$ 150	$ 250	$ 300
Provisions for doubtful accounts	47	39	21
Charge-offs, net of recoveries	(47)	(139)	(71)
Balance at end of year	$ 150	$ 150	$ 250