Acquisition - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	1 Months Ended	3 Months Ended		9 Months Ended
	Feb. 28, 2013	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Business Acquisition [Line Items]
Aggregate business acquisition purchase price	$ 37,827				$ 37,827
Revenue		64,245	61,133	192,607	178,291
Net income		17,504	18,213	53,170	52,883
Xtrakter Limited [Member]
Business Acquisition [Line Items]
Aggregate business acquisition purchase price	37,800
Revenue					12,800
Net income					$ 100