Segment and Geographical Information - Schedule of Revenues Attributed to Geographic Location (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting, Revenue Reconciling Item [Line Items]
Total consolidated revenues	$ 53,627	$ 51,013	$ 53,167	$ 49,173	$ 53,065	$ 50,196	$ 51,020	$ 50,443	$ 206,980	$ 204,724	$ 196,278
UNITED STATES
Segment Reporting, Revenue Reconciling Item [Line Items]
Total consolidated revenues									137,060	134,951	130,476
International [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Total consolidated revenues									$ 69,920	$ 69,773	$ 65,802