Revenues and Assets from External Customers (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenues From External Customers And Long Lived Assets [Line Items]
Revenue from external customers	$ 76,963	$ 63,716	$ 52,886	$ 55,054	$ 55,365	$ 54,045	$ 54,881	$ 56,217	$ 248,619	$ 220,508	$ 211,661
Long-lived assets	37,336				23,678				37,336	23,678	25,815
UNITED STATES
Revenues From External Customers And Long Lived Assets [Line Items]
Revenue from external customers									248,619	220,508	209,310
Long-lived assets	$ 37,336				$ 23,678				$ 37,336	$ 23,678	25,660
Other countries within Americas reporting unit
Revenues From External Customers And Long Lived Assets [Line Items]
Revenue from external customers											2,351
Other Countries
Revenues From External Customers And Long Lived Assets [Line Items]
Long-lived assets											$ 155