Derivative Financial Instruments - Master Netting Arrangements (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Assets and Liabilities Subject to Master Netting Arrangements [Line Items]
Gross Amounts of Recognized Assets	$ 488,754	$ 356,265
Gross Amounts offset in the Statement of Financial Position	0	0
Gross Amounts of Recognized Liabilities	117,694	108,581
Net Amounts of Assets Presented in the Statement of Financial Position	488,754	356,265
Gross Assets Subject To Master Netting Arrangement Not Offset	(395,975)	(274,630)
Cash Collateral Received Subject to Master Netting Arrangements	(7,140)	(3,730)
Net Assets After Deducting Amounts Subject to Master Netting Arrangements	85,639	77,905
Gross Amounts offset in the Statement of Financial Position	0	0
Cash Collateral Pledged Subject to Master Netting Arrangements	(96,214)	(81,164)
Securities Sold under Agreements to Repurchase, Asset	0	0
Net Amounts of Liabilities Presented in the Statement of Financial Position	117,694	108,581
Gross Liabilities Subject To Master Netting Arrangement Not Offset	(7,586)	(11,498)
Net Liabilities After Deducting Amounts Subject to Master Netting Arrangements	13,894	15,919
Securities Sold under Agreements to Repurchase, Gross	0	0
Securities Purchased under Agreements to Resell, Gross	375,180	247,876
Securities Purchased under Agreements to Resell, Liability	0	0
Securities Purchased under Agreements to Resell, Collateral, Obligation to Return Securities	375,180	247,876
Securities Purchased under Agreements to Resell, Collateral, Obligation to Return Cash	0	0
Securities Sold under Agreements to Repurchase, Collateral, Right to Reclaim Securities	0	0
Securities Sold under Agreements to Repurchase, Collateral, Right to Reclaim Cash	0	0
Foreign exchange forwards
Assets and Liabilities Subject to Master Netting Arrangements [Line Items]
Derivative Asset, Fair Value, Gross Asset	106,618	95,449
Derivative Asset, Fair Value, Gross Liability	0	0
Fair value, Liabilities	(102,439)	(95,454)
Derivative Liability, Fair Value, Gross Asset	0	0
Derivative, Collateral, Obligation to Return Securities	17,027	14,570
Derivative, Collateral, Obligation to Return Cash	5,264	3,616
Derivative, Collateral, Right to Reclaim Securities	6,624	10,997
Derivative, Collateral, Right to Reclaim Cash	82,502	69,110
Client foreign currency options
Assets and Liabilities Subject to Master Netting Arrangements [Line Items]
Derivative Asset, Fair Value, Gross Asset	1,886	1,187
Derivative Asset, Fair Value, Gross Liability	0	0
Fair value, Liabilities	(1,886)	(1,187)
Derivative Liability, Fair Value, Gross Asset	0	0
Derivative, Collateral, Obligation to Return Securities	574	557
Derivative, Collateral, Obligation to Return Cash	0	0
Derivative, Collateral, Right to Reclaim Securities	962	501
Derivative, Collateral, Right to Reclaim Cash	434	130
Client interest rate derivatives
Assets and Liabilities Subject to Master Netting Arrangements [Line Items]
Derivative Asset, Fair Value, Gross Asset	5,070	11,753
Derivative Asset, Fair Value, Gross Liability	0	0
Fair value, Liabilities	(13,369)	(11,940)
Derivative Liability, Fair Value, Gross Asset	0	0
Derivative, Collateral, Obligation to Return Securities	3,194	11,627
Derivative, Collateral, Obligation to Return Cash	1,876	114
Derivative, Collateral, Right to Reclaim Securities	0	0
Derivative, Collateral, Right to Reclaim Cash	13,278	11,924
Derivative
Assets and Liabilities Subject to Master Netting Arrangements [Line Items]
Gross Amounts of Recognized Assets	113,574	108,389
Gross Amounts offset in the Statement of Financial Position	0	0
Gross Amounts of Recognized Liabilities	117,694	108,581
Net Amounts of Assets Presented in the Statement of Financial Position	113,574	108,389
Gross Assets Subject To Master Netting Arrangement Not Offset	(20,795)	(26,754)
Cash Collateral Received Subject to Master Netting Arrangements	(7,140)	(3,730)
Net Assets After Deducting Amounts Subject to Master Netting Arrangements	85,639	77,905
Gross Amounts offset in the Statement of Financial Position	0	0
Cash Collateral Pledged Subject to Master Netting Arrangements	(96,214)	(81,164)
Net Amounts of Liabilities Presented in the Statement of Financial Position	117,694	108,581
Gross Liabilities Subject To Master Netting Arrangement Not Offset	(7,586)	(11,498)
Net Liabilities After Deducting Amounts Subject to Master Netting Arrangements	13,894	15,919
Derivative | Foreign exchange forwards
Assets and Liabilities Subject to Master Netting Arrangements [Line Items]
Net Amounts of Assets Presented in the Statement of Financial Position	106,618	95,449
Net Assets After Deducting Amounts Subject to Master Netting Arrangements	84,327	77,263
Net Amounts of Liabilities Presented in the Statement of Financial Position	102,439	95,454
Net Liabilities After Deducting Amounts Subject to Master Netting Arrangements	13,313	15,347
Derivative | Client foreign currency options
Assets and Liabilities Subject to Master Netting Arrangements [Line Items]
Net Amounts of Assets Presented in the Statement of Financial Position	1,886	1,187
Net Assets After Deducting Amounts Subject to Master Netting Arrangements	1,312	630
Net Amounts of Liabilities Presented in the Statement of Financial Position	1,886	1,187
Net Liabilities After Deducting Amounts Subject to Master Netting Arrangements	490	556
Derivative | Client interest rate derivatives
Assets and Liabilities Subject to Master Netting Arrangements [Line Items]
Net Amounts of Assets Presented in the Statement of Financial Position	5,070	11,753
Net Assets After Deducting Amounts Subject to Master Netting Arrangements	0	12
Net Amounts of Liabilities Presented in the Statement of Financial Position	13,369	11,940
Net Liabilities After Deducting Amounts Subject to Master Netting Arrangements	91	16
Reverse Repurchase Securities Borrowing And Similar Arrangements
Assets and Liabilities Subject to Master Netting Arrangements [Line Items]
Net Amounts of Assets Presented in the Statement of Financial Position	375,180	247,876
Net Assets After Deducting Amounts Subject to Master Netting Arrangements	0	0
Net Amounts of Liabilities Presented in the Statement of Financial Position	0	0
Net Liabilities After Deducting Amounts Subject to Master Netting Arrangements	0	0
Other assets | Derivatives not designated as hedging instruments | Equity warrant assets | Other derivative instruments
Assets and Liabilities Subject to Master Netting Arrangements [Line Items]
Derivative, Notional Amount	222,373	211,253
Derivative Asset, Fair Value, Gross Asset	$ 135,669	$ 123,763