Fair Value of Financial Assets and Liabilities - Fair Value Hierarchy of Financial Assets and Liabilities under FASB Guidance (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Net amounts of recognized assets
Marketable securities, Assets	$ 169,241	$ 164,820
Government debt, Assets	33,621	35,190
Securities owned - Equities, Assets	122	167
Forwards, Assets	169	35
Foreign exchange swaps, Assets	2,816	2,946
Interest rate swaps, Assets	227	202
Foreign exchange/commodities options, Assets		244
Total, Assets	206,196	203,604
Net amounts of recognized Liabilities
Forwards, Liabilities	65	36
Futures, Liabilities	1,734	512
Foreign exchange/commodities options, Liabilities	1,588	41
Foreign exchange swaps, Liabilities	3,964	977
Contingent consideration, Liabilities	58,396	55,614
Total, Liabilities	65,747	57,180
Netting and Collateral [Member]
Net amounts of recognized assets
Forwards, Assets	(1)	(22)
Foreign exchange swaps, Assets	(325)	(495)
Interest rate swaps, Assets		(29)
Total, Assets	(326)	(546)
Net amounts of recognized Liabilities
Forwards, Liabilities	(1)	(22)
Interest rate swaps, Liabilities		(29)
Foreign exchange swaps, Liabilities	(325)	(495)
Total, Liabilities	(326)	(546)
Level 1 [Member]
Net amounts of recognized assets
Marketable securities, Assets	169,241	164,820
Government debt, Assets	33,621	35,190
Securities owned - Equities, Assets	122	167
Foreign exchange/commodities options, Assets		244
Total, Assets	202,984	200,421
Net amounts of recognized Liabilities
Foreign exchange/commodities options, Liabilities	1,588	41
Total, Liabilities	1,588	41
Level 2 [Member]
Net amounts of recognized assets
Forwards, Assets	170	57
Foreign exchange swaps, Assets	3,141	3,441
Interest rate swaps, Assets	227	231
Total, Assets	3,538	3,729
Net amounts of recognized Liabilities
Forwards, Liabilities	66	58
Futures, Liabilities	1,734	512
Interest rate swaps, Liabilities		29
Foreign exchange swaps, Liabilities	4,289	1,472
Total, Liabilities	6,089	2,071
Level 3 [Member]
Net amounts of recognized Liabilities
Contingent consideration, Liabilities	58,396	55,614
Total, Liabilities	$ 58,396	$ 55,614