Assets & Liability Derivative Positions & the Potential Effect of Netting Arrangements - Current Quarter (Details) - USD ($) $ in Thousands		Sep. 30, 2018	Dec. 31, 2017
Offsetting Liabilities [Line Items]
Derivative Asset, Fair Value, Gross Asset		$ 29,768	$ 17,318
Derivative Asset, Collateral, Obligation to Return Cash, Offset		0	0
Derivative Asset		29,768	17,318
Derivative, Collateral, Obligation to Return Securities	[1]	3,598	5,383
Derivative, Collateral, Obligation to Return Cash		(13,738)	0
Derivative Asset, Fair Value, Amount Offset Against Collateral		12,432	11,935
Derivative Liability, Fair Value, Gross Liability		28,385	15,693
Derivative Liability, Collateral, Right to Reclaim Cash, Offset		0	0
Derivative Liability		28,385	15,693
Derivative, Collateral, Right to Reclaim Securities	[1]	3,598	5,383
Derivative, Collateral, Right to Reclaim Cash		22	3,939
Derivative Liability, Fair Value, Amount Offset Against Collateral		24,765	6,371
Interest rate swaps
Offsetting Liabilities [Line Items]
Derivative Asset, Collateral, Obligation to Return Cash, Offset		0	0
Derivative Asset		3,584	1,880
Derivative, Collateral, Obligation to Return Securities	[1]	2,189	805
Derivative, Collateral, Obligation to Return Cash		(1,133)	0
Derivative Asset, Fair Value, Amount Offset Against Collateral		262	1,075
Derivative Liability, Collateral, Right to Reclaim Cash, Offset		0	0
Derivative Liability		2,209	264
Derivative, Collateral, Right to Reclaim Securities	[1]	2,189	0
Derivative, Collateral, Right to Reclaim Cash		20	264
Derivative Liability, Fair Value, Amount Offset Against Collateral		0	0
Loan level swaps
Offsetting Liabilities [Line Items]
Derivative Asset, Collateral, Obligation to Return Cash, Offset		0	0
Derivative Asset		25,041	14,236
Derivative, Collateral, Obligation to Return Securities	[1]	1,409	4,578
Derivative, Collateral, Obligation to Return Cash		(12,605)	0
Derivative Asset, Fair Value, Amount Offset Against Collateral		11,027	9,658
Derivative Liability, Collateral, Right to Reclaim Cash, Offset		0	0
Derivative Liability		25,055	14,241
Derivative, Collateral, Right to Reclaim Securities	[1]	1,409	5,383
Derivative, Collateral, Right to Reclaim Cash		2	3,675
Derivative Liability, Fair Value, Amount Offset Against Collateral		23,644	5,183
Customer foreign exchange contracts
Offsetting Liabilities [Line Items]
Derivative Asset, Collateral, Obligation to Return Cash, Offset		0	0
Derivative Asset		1,143	1,202
Derivative, Collateral, Obligation to Return Securities	[1]	0	0
Derivative, Collateral, Obligation to Return Cash		0	0
Derivative Asset, Fair Value, Amount Offset Against Collateral		1,143	1,202
Derivative Liability, Collateral, Right to Reclaim Cash, Offset		0	0
Derivative Liability		1,121	1,188
Derivative, Collateral, Right to Reclaim Securities	[1]	0	0
Derivative, Collateral, Right to Reclaim Cash		0	0
Derivative Liability, Fair Value, Amount Offset Against Collateral		1,121	1,188
Other Assets [Member]
Offsetting Liabilities [Line Items]
Derivative Asset, Fair Value, Gross Asset		30,001	17,476
Other Assets [Member] | Loan level swaps
Offsetting Liabilities [Line Items]
Derivative Asset, Fair Value, Gross Asset		25,041	14,236
Other Assets [Member] | Customer foreign exchange contracts
Offsetting Liabilities [Line Items]
Derivative Asset, Fair Value, Gross Asset		1,143	1,202
Other Liabilities [Member]
Offsetting Liabilities [Line Items]
Derivative Liability, Fair Value, Gross Liability		28,446	15,693
Other Liabilities [Member] | Loan level swaps
Offsetting Liabilities [Line Items]
Derivative Liability, Fair Value, Gross Liability		25,055	14,241
Other Liabilities [Member] | Customer foreign exchange contracts
Offsetting Liabilities [Line Items]
Derivative Liability, Fair Value, Gross Liability		1,121	1,188
Designated as Hedging Instrument [Member] | Other Assets [Member] | Interest rate swaps
Offsetting Liabilities [Line Items]
Interest Rate Derivative Assets, at Fair Value		3,584	1,880
Designated as Hedging Instrument [Member] | Other Liabilities [Member] | Interest rate swaps
Offsetting Liabilities [Line Items]
Interest Rate Derivative Liabilities, at Fair Value		2,209	264
Customer repurchase agreements and other short-term borrowings(f)
Offsetting Liabilities [Line Items]
Securities Sold under Agreements to Repurchase, Collateral, Right to Reclaim Securities		0	0
Securities Sold under Agreements to Repurchase, Gross Including Not Subject to Master Netting Arrangement		141,176	162,679
Securities Sold under Agreements to Repurchase, Asset		0	0
Securities Sold under Agreements to Repurchase, Not Subject to Master Netting Arrangement		141,176	162,679
Securities Sold under Agreements to Repurchase, Fair Value of Collateral		141,176	162,679
Securities Sold under Agreements to Repurchase, Amount Offset Against Collateral		$ 0	$ 0

[1] Reflects offsetting derivative positions with the same counterparty.