Revenues by Geographic Territory (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Segment Reporting Information [Line Items]
Revenues	$ 28,497	$ 30,637	$ 30,689	$ 29,239	$ 25,519	$ 30,457	$ 31,139	$ 30,589	$ 119,062	$ 117,704	$ 108,569
United States
Segment Reporting Information [Line Items]
Revenues									69,388	68,156	64,854
Canada
Segment Reporting Information [Line Items]
Revenues									13,352	17,524	17,792
Other Countries less than 10% of revenues
Segment Reporting Information [Line Items]
Revenues									$ 36,322	$ 32,024	$ 25,923