Fair Value Measurements - Additional Information (Detail)	1 Months Ended	3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended					9 Months Ended	12 Months Ended
	Mar. 31, 2014 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2014 General and Administrative [Member] USD ($)	Sep. 30, 2014 General and Administrative [Member] USD ($)	Sep. 30, 2014 Forward Contract to Sell [Member] GBP (£) Contract	Dec. 31, 2013 Forward Contract to Sell [Member] GBP (£) Contract	Sep. 30, 2014 Forward Contract to Purchase [Member] USD ($) Contract	Dec. 31, 2013 Forward Contract to Purchase [Member] USD ($) Contract	Sep. 30, 2014 Forward Contracts [Member]	Dec. 31, 2013 Forward Contracts [Member]
Derivative [Line Items]
30-day forward contract outstanding						£ 2,400,000	£ 3,000,000	$ 3,900,000	$ 5,000,000
Number of forward contracts outstanding						1	1	1	1
Forward contract terms										30-day forward contract	30-day forward contract
Decrease in the contingent acquisition consideration	$ 400,000	$ 600,000	$ 1,152,000	$ 600,000	$ 1,200,000