Fair Value of Financial Assets and Liabilities - Fair Value Hierarchy of Financial Assets and Liabilities under FASB Guidance (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Net amounts of recognized assets
Loans held for sale, Assets	$ 660,332	$ 1,071,836
Marketable securities, Assets	259,442	164,820
Government debt, Assets	32,019	35,190
Securities owned - Equities, Assets	102	167
Forwards, Assets	6,436	17,859
Rate lock commitments, Assets	4,678	2,100
Foreign exchange swaps, Assets	3,129	2,946
Foreign exchange/commodities options, Assets	1,013	244
Interest rate swaps, Assets	245	202
Futures, Assets	67
Total, Assets	967,463	1,295,364
Net amounts of recognized Liabilities
Foreign exchange swaps, Liabilities	1,740	977
Rate lock commitments, Liabilities	863	9,670
Forwards, Liabilities	594	36
Futures, Liabilities	442	512
Foreign exchange/commodities options, Liabilities	313	41
Contingent consideration, Liabilities	71,406	66,004
Total, Liabilities	75,358	77,240
Netting and Collateral [Member]
Net amounts of recognized assets
Forwards, Assets	(2)	(22)
Foreign exchange swaps, Assets	(949)	(495)
Total, Assets	(951)	(517)
Net amounts of recognized Liabilities
Foreign exchange swaps, Liabilities	(949)	(495)
Forwards, Liabilities	(2)	(22)
Total, Liabilities	(951)	(517)
Level 1 [Member]
Net amounts of recognized assets
Marketable securities, Assets	259,442	164,820
Government debt, Assets	32,019	35,190
Securities owned - Equities, Assets	102	167
Foreign exchange/commodities options, Assets	1,013	244
Total, Assets	292,576	200,421
Net amounts of recognized Liabilities
Foreign exchange/commodities options, Liabilities	313	41
Total, Liabilities	313	41
Level 2 [Member]
Net amounts of recognized assets
Loans held for sale, Assets	660,332	1,071,836
Forwards, Assets	16	57
Foreign exchange swaps, Assets	4,078	3,441
Interest rate swaps, Assets	245	202
Futures, Assets	67
Total, Assets	664,738	1,075,536
Net amounts of recognized Liabilities
Foreign exchange swaps, Liabilities	2,689	1,472
Forwards, Liabilities	429	58
Futures, Liabilities	442	512
Total, Liabilities	3,560	2,042
Level 3 [Member]
Net amounts of recognized assets
Forwards, Assets	6,422	17,824
Rate lock commitments, Assets	4,678	2,100
Total, Assets	11,100	19,924
Net amounts of recognized Liabilities
Rate lock commitments, Liabilities	863	9,670
Forwards, Liabilities	167
Contingent consideration, Liabilities	71,406	66,004
Total, Liabilities	$ 72,436	$ 75,674