Derivative Financial Instruments - Balance Sheet Offsetting, Assets (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Derivative Assets
Gross Amounts of Recognized Assets	$ 105,780	$ 108,389
Gross Amounts offset in the Statement of Financial Position	0	0
Net Amounts of Assets Presented in the Statement of Financial Position	105,780	108,389
Financial Instruments (Collateral)	(37,192)	(26,754)
Cash Collateral Received	(17,246)	(3,730)
Net Amount	51,342	77,905
Reverse repurchase, securities borrowing, and similar arrangements
Gross Amounts of Recognized Assets	37,379	247,876
Gross Amounts offset in the Statement of Financial Position	0	0
Net Amounts of Assets Presented in the Statement of Financial Position	37,379	247,876
Financial Instruments (Collateral)	(37,379)	(247,876)
Cash Collateral Received	0	0
Net Amount	0	0
Total
Gross Amounts of Recognized Assets	143,159	356,265
Gross Amounts offset in the Statement of Financial Position	0	0
Net Amounts of Assets Presented in the Statement of Financial Position	143,159	356,265
Financial Instruments (Collateral)	(74,571)	(274,630)
Cash Collateral Received	(17,246)	(3,730)
Net Amount	51,342	77,905
Foreign exchange forwards
Derivative Assets
Gross Amounts of Recognized Assets	97,645	95,449
Gross Amounts offset in the Statement of Financial Position	0	0
Net Amounts of Assets Presented in the Statement of Financial Position	97,645	95,449
Financial Instruments (Collateral)	(32,627)	(14,570)
Cash Collateral Received	(14,416)	(3,616)
Net Amount	50,602	77,263
Client foreign currency options
Derivative Assets
Gross Amounts of Recognized Assets	1,713	1,187
Gross Amounts offset in the Statement of Financial Position	0	0
Net Amounts of Assets Presented in the Statement of Financial Position	1,713	1,187
Financial Instruments (Collateral)	(973)	(557)
Cash Collateral Received	0	0
Net Amount	740	630
Client interest rate derivatives
Derivative Assets
Gross Amounts of Recognized Assets	6,422	11,753
Gross Amounts offset in the Statement of Financial Position	0	0
Net Amounts of Assets Presented in the Statement of Financial Position	6,422	11,753
Financial Instruments (Collateral)	(3,592)	(11,627)
Cash Collateral Received	(2,830)	(114)
Net Amount	$ 0	$ 12