Fair Value of Financial Assets and Liabilities - Fair Value Hierarchy of Financial Assets and Liabilities under FASB Guidance (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Net amounts of recognized assets
Marketable securities, Assets	$ 163,208	$ 164,820
Government debt, Assets	33,777	35,190
Securities owned - Equities, Assets	311	167
Forwards, Assets	12	35
Foreign exchange swaps, Assets	3,926	2,946
Interest rate swaps, Assets	234	202
Foreign exchange/commodities options, Assets		244
Total, Assets	201,468	203,604
Net amounts of recognized Liabilities
Forwards, Liabilities	3,219	36
Futures, Liabilities	2,037	512
Foreign exchange/commodities options, Liabilities	80	41
Foreign exchange swaps, Liabilities	5,698	977
Contingent consideration, Liabilities	52,737	55,614
Total, Liabilities	63,771	57,180
Netting and Collateral [Member]
Net amounts of recognized assets
Forwards, Assets		(22)
Foreign exchange swaps, Assets	(468)	(495)
Interest rate swaps, Assets	(3)	(29)
Total, Assets	(471)	(546)
Net amounts of recognized Liabilities
Forwards, Liabilities		(22)
Foreign exchange swaps, Liabilities	(468)	(495)
Interest rate swaps, Liabilities	(3)	(29)
Total, Liabilities	(471)	(546)
Level 1 [Member]
Net amounts of recognized assets
Marketable securities, Assets	163,208	164,820
Government debt, Assets	33,777	35,190
Securities owned - Equities, Assets	311	167
Foreign exchange/commodities options, Assets		244
Total, Assets	197,296	200,421
Net amounts of recognized Liabilities
Foreign exchange/commodities options, Liabilities	80	41
Total, Liabilities	80	41
Level 2 [Member]
Net amounts of recognized assets
Forwards, Assets	12	57
Foreign exchange swaps, Assets	4,394	3,441
Interest rate swaps, Assets	237	231
Total, Assets	4,643	3,729
Net amounts of recognized Liabilities
Forwards, Liabilities	3,219	58
Futures, Liabilities	2,037	512
Foreign exchange swaps, Liabilities	6,166	1,472
Interest rate swaps, Liabilities	3	29
Total, Liabilities	11,425	2,071
Level 3 [Member]
Net amounts of recognized Liabilities
Contingent consideration, Liabilities	52,737	55,614
Total, Liabilities	$ 52,737	$ 55,614