Derivative Financial Instruments - Balance Sheet Offsetting, Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Derivative Liabilities
Gross Amounts of Recognized Liabilities	$ 91,321	$ 108,581
Gross Amounts offset in the Statement of Financial Position	0	0
Net Amounts of Liabilities Presented in the Statement of Financial Position	91,321	108,581
Financial Instruments (Collateral)	(27,586)	(11,498)
Cash Collateral Pledged	(30,216)	(81,164)
Net Amount	33,519	15,919
Repurchase, securities lending, and similar arrangements
Securities Sold under Agreements to Repurchase, Gross	371,539	0
Securities Sold under Agreements to Repurchase, Asset	0	0
Securities Sold under Agreements to Repurchase	371,539	0
Financial Instruments (Collateral)	(147,757)	0
Cash Collateral Pledged	(750)	0
Net Amount	223,032	0
Total
Gross Amounts of Recognized Liabilities	462,860	108,581
Gross Amounts offset in the Statement of Financial Position	0	0
Net Amounts of Liabilities Presented in the Statement of Financial Position	462,860	108,581
Financial Instruments (Collateral)	(175,343)	(11,498)
Cash Collateral Pledged	(30,966)	(81,164)
Net Amount	256,551	15,919
Foreign exchange forwards
Derivative Liabilities
Gross Amounts of Recognized Liabilities	74,687	95,454
Gross Amounts offset in the Statement of Financial Position	0	0
Net Amounts of Liabilities Presented in the Statement of Financial Position	74,687	95,454
Financial Instruments (Collateral)	(22,038)	(10,997)
Cash Collateral Pledged	(20,036)	(69,110)
Net Amount	32,613	15,347
Client foreign currency options
Derivative Liabilities
Gross Amounts of Recognized Liabilities	1,478	1,187
Gross Amounts offset in the Statement of Financial Position	0	0
Net Amounts of Liabilities Presented in the Statement of Financial Position	1,478	1,187
Financial Instruments (Collateral)	(666)	(501)
Cash Collateral Pledged	0	(130)
Net Amount	812	556
Client interest rate derivatives
Derivative Liabilities
Gross Amounts of Recognized Liabilities	15,156	11,940
Gross Amounts offset in the Statement of Financial Position	0	0
Net Amounts of Liabilities Presented in the Statement of Financial Position	15,156	11,940
Financial Instruments (Collateral)	(4,882)	0
Cash Collateral Pledged	(10,180)	(11,924)
Net Amount	$ 94	$ 16