Assets & Liability Derivative Positions & the Potential Effect of Netting Arrangements - Current Quarter (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Offsetting Liabilities [Line Items]
Derivative Asset, Fair Value, Gross Asset	$ 20,029	$ 22,331
Derivative Asset, Collateral, Obligation to Return Cash, Offset	0	0
Derivative Asset	20,029	22,331
Derivative, Collateral, Obligation to Return Securities	4,087	4,222
Derivative, Collateral, Obligation to Return Cash	0	0
Derivative Asset, Fair Value, Amount Offset Against Collateral	15,942	18,109
Derivative Liability, Fair Value, Gross Liability	198,863	198,596
Derivative Liability, Collateral, Right to Reclaim Cash, Offset	0	0
Derivative Liability	198,863	198,596
Derivative, Collateral, Right to Reclaim Securities	4,087	4,222
Derivative, Collateral, Right to Reclaim Cash	189,931	188,759
Derivative Liability, Fair Value, Amount Offset Against Collateral	4,845	5,615
Interest rate swaps
Offsetting Liabilities [Line Items]
Derivative Asset, Fair Value, Gross Asset		1,364
Derivative Asset, Collateral, Obligation to Return Cash, Offset	0	0
Derivative Asset	1,229	1,364
Derivative, Collateral, Obligation to Return Securities	1,229	961
Derivative, Collateral, Obligation to Return Cash	0	0
Derivative Asset, Fair Value, Amount Offset Against Collateral	0	403
Derivative Liability, Fair Value, Gross Liability		740
Derivative Liability, Collateral, Right to Reclaim Cash, Offset	0	0
Derivative Liability	407	740
Derivative, Collateral, Right to Reclaim Securities	0	0
Derivative, Collateral, Right to Reclaim Cash	407	740
Derivative Liability, Fair Value, Amount Offset Against Collateral	0	0
Loan level swaps
Offsetting Liabilities [Line Items]
Derivative Asset, Fair Value, Gross Asset		18,629
Derivative Asset, Collateral, Obligation to Return Cash, Offset	0	0
Derivative Asset	16,991	18,629
Derivative, Collateral, Obligation to Return Securities	2,858	3,261
Derivative, Collateral, Obligation to Return Cash	0	0
Derivative Asset, Fair Value, Amount Offset Against Collateral	14,133	15,368
Derivative Liability, Fair Value, Gross Liability		18,632
Derivative Liability, Collateral, Right to Reclaim Cash, Offset	0	0
Derivative Liability	16,992	18,632
Derivative, Collateral, Right to Reclaim Securities	4,087	4,222
Derivative, Collateral, Right to Reclaim Cash	9,854	11,106
Derivative Liability, Fair Value, Amount Offset Against Collateral	3,051	3,304
Customer foreign exchange contracts
Offsetting Liabilities [Line Items]
Derivative Asset, Fair Value, Gross Asset		2,338
Derivative Asset, Collateral, Obligation to Return Cash, Offset	0	0
Derivative Asset	1,809	2,338
Derivative, Collateral, Obligation to Return Securities	0	0
Derivative, Collateral, Obligation to Return Cash	0	0
Derivative Asset, Fair Value, Amount Offset Against Collateral	1,809	2,338
Derivative Liability, Fair Value, Gross Liability		2,311
Derivative Liability, Collateral, Right to Reclaim Cash, Offset	0	0
Derivative Liability	1,794	2,311
Derivative, Collateral, Right to Reclaim Securities	0	0
Derivative, Collateral, Right to Reclaim Cash	0	0
Derivative Liability, Fair Value, Amount Offset Against Collateral	1,794	2,311
Customer repurchase agreements and other short-term borrowings(f)
Offsetting Liabilities [Line Items]
Derivative Liability, Fair Value, Gross Liability	179,670	176,913
Derivative Liability, Collateral, Right to Reclaim Cash, Offset	0	0
Derivative Liability	179,670	176,913
Derivative, Collateral, Right to Reclaim Securities	0	0
Derivative, Collateral, Right to Reclaim Cash	179,670	176,913
Derivative Liability, Fair Value, Amount Offset Against Collateral	0	0
Other Assets [Member]
Offsetting Liabilities [Line Items]
Derivative Asset, Fair Value, Gross Asset	20,303	22,761
Other Assets [Member] | Loan level swaps
Offsetting Liabilities [Line Items]
Derivative Asset, Fair Value, Gross Asset	16,991	18,629
Other Assets [Member] | Customer foreign exchange contracts
Offsetting Liabilities [Line Items]
Derivative Asset, Fair Value, Gross Asset	1,809	2,338
Other Liabilities [Member]
Offsetting Liabilities [Line Items]
Derivative Liability, Fair Value, Gross Liability	19,199	21,916
Other Liabilities [Member] | Loan level swaps
Offsetting Liabilities [Line Items]
Derivative Liability, Fair Value, Gross Liability	16,992	18,632
Other Liabilities [Member] | Customer foreign exchange contracts
Offsetting Liabilities [Line Items]
Derivative Liability, Fair Value, Gross Liability	1,794	2,311
Designated as Hedging Instrument [Member] | Other Assets [Member] | Interest rate swaps
Offsetting Liabilities [Line Items]
Interest Rate Derivative Assets, at Fair Value	1,229	1,364
Designated as Hedging Instrument [Member] | Other Liabilities [Member] | Interest rate swaps
Offsetting Liabilities [Line Items]
Interest Rate Derivative Liabilities, at Fair Value	$ 407	$ 740