Assets & Liability Derivative Positions & the Potential Effect of Netting Arrangements - Current Quarter (Details) - USD ($) $ in Thousands		Mar. 31, 2018	Dec. 31, 2017
Offsetting Liabilities [Line Items]
Derivative Asset, Fair Value, Gross Asset		$ 20,870	$ 17,318
Derivative Asset, Collateral, Obligation to Return Cash, Offset		0	0
Derivative Asset		20,870	17,318
Derivative, Collateral, Obligation to Return Securities	[1]	3,715	5,383
Derivative, Collateral, Obligation to Return Cash		(10,073)	0
Derivative Asset, Fair Value, Amount Offset Against Collateral		7,082	11,935
Derivative Liability, Fair Value, Gross Liability		18,891	15,693
Derivative Liability, Collateral, Right to Reclaim Cash, Offset		0	0
Derivative Liability		18,891	15,693
Derivative, Collateral, Right to Reclaim Securities	[1]	3,715	5,383
Derivative, Collateral, Right to Reclaim Cash		259	3,939
Derivative Liability, Fair Value, Amount Offset Against Collateral		14,917	6,371
Interest rate swaps
Offsetting Liabilities [Line Items]
Derivative Asset, Collateral, Obligation to Return Cash, Offset		0	0
Derivative Asset		3,040	1,880
Derivative, Collateral, Obligation to Return Securities	[1]	948	805
Derivative, Collateral, Obligation to Return Cash		(1,128)	0
Derivative Asset, Fair Value, Amount Offset Against Collateral		964	1,075
Derivative Liability, Collateral, Right to Reclaim Cash, Offset		0	0
Derivative Liability		1,066	264
Derivative, Collateral, Right to Reclaim Securities	[1]	948	0
Derivative, Collateral, Right to Reclaim Cash		118	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		16,916	14,236
Derivative, Collateral, Obligation to Return Securities	[1]	2,767	4,578
Derivative, Collateral, Obligation to Return Cash		(8,945)	0
Derivative Asset, Fair Value, Amount Offset Against Collateral		5,204	9,658
Derivative Liability, Collateral, Right to Reclaim Cash, Offset		0	0
Derivative Liability		16,930	14,241
Derivative, Collateral, Right to Reclaim Securities	[1]	2,767	5,383
Derivative, Collateral, Right to Reclaim Cash		141	3,675
Derivative Liability, Fair Value, Amount Offset Against Collateral		14,022	5,183
Customer foreign exchange contracts
Offsetting Liabilities [Line Items]
Derivative Asset, Collateral, Obligation to Return Cash, Offset		0	0
Derivative Asset		914	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		914	1,202
Derivative Liability, Collateral, Right to Reclaim Cash, Offset		0	0
Derivative Liability		895	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		895	1,188
Other Assets [Member]
Offsetting Liabilities [Line Items]
Derivative Asset, Fair Value, Gross Asset		21,040	17,476
Other Assets [Member] | Loan level swaps
Offsetting Liabilities [Line Items]
Derivative Asset, Fair Value, Gross Asset		16,916	14,236
Other Assets [Member] | Customer foreign exchange contracts
Offsetting Liabilities [Line Items]
Derivative Asset, Fair Value, Gross Asset		914	1,202
Other Liabilities [Member]
Offsetting Liabilities [Line Items]
Derivative Liability, Fair Value, Gross Liability		18,891	15,693
Other Liabilities [Member] | Loan level swaps
Offsetting Liabilities [Line Items]
Derivative Liability, Fair Value, Gross Liability		16,930	14,241
Other Liabilities [Member] | Customer foreign exchange contracts
Offsetting Liabilities [Line Items]
Derivative Liability, Fair Value, Gross Liability		895	1,188
Designated as Hedging Instrument [Member] | Other Assets [Member] | Interest rate swaps
Offsetting Liabilities [Line Items]
Interest Rate Derivative Assets, at Fair Value		3,040	1,880
Designated as Hedging Instrument [Member] | Other Liabilities [Member] | Interest rate swaps
Offsetting Liabilities [Line Items]
Interest Rate Derivative Liabilities, at Fair Value		1,066	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		137,914	162,679
Securities Sold under Agreements to Repurchase, Asset		0	0
Securities Sold under Agreements to Repurchase, Not Subject to Master Netting Arrangement		137,914	162,679
Securities Sold under Agreements to Repurchase, Fair Value of Collateral		137,914	162,679
Securities Sold under Agreements to Repurchase, Amount Offset Against Collateral		$ 0	$ 0

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