Derivative Financial Instruments - Balance Sheet Offsetting, Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Derivative Assets
Gross Amounts of Recognized Assets	$ 88,165	$ 108,389
Gross Amounts offset in the Statement of Financial Position	0	0
Net Amounts of Assets Presented in the Statement of Financial Position	88,165	108,389
Financial Instruments (Collateral)	(33,576)	(26,754)
Cash Collateral Received	(9,713)	(3,730)
Net Amount	44,876	77,905
Reverse repurchase, securities borrowing, and similar arrangements
Gross Amounts of Recognized Assets	119,181	247,876
Gross Amounts offset in the Statement of Financial Position	0	0
Net Amounts of Assets Presented in the Statement of Financial Position	119,181	247,876
Financial Instruments (Collateral)	(119,181)	(247,876)
Cash Collateral Received	0	0
Net Amount	0	0
Total
Gross Amounts of Recognized Assets	207,346	356,265
Gross Amounts offset in the Statement of Financial Position	0	0
Net Amounts of Assets Presented in the Statement of Financial Position	207,346	356,265
Financial Instruments (Collateral)	(152,757)	(274,630)
Cash Collateral Received	(9,713)	(3,730)
Net Amount	44,876	77,905
Foreign exchange forwards
Derivative Assets
Gross Amounts of Recognized Assets	80,427	95,449
Gross Amounts offset in the Statement of Financial Position	0	0
Net Amounts of Assets Presented in the Statement of Financial Position	80,427	95,449
Financial Instruments (Collateral)	(29,400)	(14,570)
Cash Collateral Received	(6,816)	(3,616)
Net Amount	44,211	77,263
Client foreign currency options
Derivative Assets
Gross Amounts of Recognized Assets	1,476	1,187
Gross Amounts offset in the Statement of Financial Position	0	0
Net Amounts of Assets Presented in the Statement of Financial Position	1,476	1,187
Financial Instruments (Collateral)	(811)	(557)
Cash Collateral Received	0	0
Net Amount	665	630
Client interest rate derivatives
Derivative Assets
Gross Amounts of Recognized Assets	6,262	11,753
Gross Amounts offset in the Statement of Financial Position	0	0
Net Amounts of Assets Presented in the Statement of Financial Position	6,262	11,753
Financial Instruments (Collateral)	(3,365)	(11,627)
Cash Collateral Received	(2,897)	(114)
Net Amount	$ 0	$ 12