Derivatives (Narrative) (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Derivative Instruments, Gain (Loss) [Line Items]
Collateral cash receivables	$ 89,800,000	$ 111,700,000	$ 89,800,000	$ 111,700,000
Collateral cash payables	68,100,000	90,100,000	68,100,000	90,100,000
Total trading revenues	41,200,000	54,400,000	131,300,000	180,900,000
Noncallable senior debt maturing date	2015-12-01
Other Long-term Debt	1,491,138,000	1,771,288,000	1,491,138,000	1,771,288,000	1,739,859,000
Hedged amount of foreign currency denominated loans		600,000		600,000
Visa Class B Shares [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative liabilities related to sale	7,600,000	2,700,000	7,600,000	2,700,000
Parent Company [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Hedged held-to-maturity trust preferred loans principal balance	6,500,000	6,500,000	6,500,000	6,500,000
Long Term Debt Hedged With Fair Value Interest Rate Derivatives Using Shortcut Method [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Net fair value of interest rate derivatives hedging	21,400,000	46,100,000	21,400,000	46,100,000
Other Long-term Debt	554,000,000	554,000,000	554,000,000	554,000,000
Long Term Debt Hedged With Fair Value Interest Rate Derivatives Using Long Haul Method [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Net fair value of interest rate derivatives hedging	11,300,000	20,000,000	11,300,000	20,000,000
Other Long-term Debt	500,000,000	500,000,000	500,000,000	500,000,000
Subordinated Debentures Subject To Mandatory Redemption Amounts Redeemed [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Net fair value of interest rate derivatives hedging subordinated debt	9,800,000	19,600,000	9,800,000	19,600,000
Other Long-term Debt	200,000,000	200,000,000	200,000,000	200,000,000
Hedge Of Held To Maturity Trust Preferred Loans [Member] | Parent Company [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Net fair value of interest rate derivatives hedging subordinated debt	800,000	1,100,000	800,000	1,100,000
Additional Derivative Agreements [Member] | Derivative Instruments With Accelerated Termination Provisions [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Collateral received	191,500,000	213,200,000	191,500,000	213,200,000
Securities posted collateral	26,300,000	24,400,000	26,300,000	24,400,000
Net fair value of derivative assets with adjustable posting thresholds	104,700,000	144,500,000	104,700,000	144,500,000
Net fair value of derivative liabilities with adjustable posting thresholds	19,100,000	27,100,000	19,100,000	27,100,000
Additional Derivative Agreements [Member] | Derivative Instruments With Adjustable Collateral Posting Thresholds [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Collateral received	191,500,000	213,200,000	191,500,000	213,200,000
Securities posted collateral	80,600,000	102,500,000	80,600,000	102,500,000
Net fair value of derivative assets with adjustable posting thresholds	104,700,000	144,500,000	104,700,000	144,500,000
Net fair value of derivative liabilities with adjustable posting thresholds	$ 77,600,000	$ 110,300,000	$ 77,600,000	$ 110,300,000