Derivatives (Narrative) (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Derivative Instruments, Gain (Loss) [Line Items]
Collateral cash receivables	$ 101,600,000	$ 111,900,000	$ 101,600,000	$ 111,900,000
Collateral cash payables	71,300,000	93,100,000	71,300,000	93,100,000
Total trading revenues	40,500,000	58,500,000	90,100,000	126,500,000
Noncallable senior debt maturing date	2015-12-01
Other Long-term Debt	1,501,209,000	1,800,255,000	1,501,209,000	1,800,255,000	1,739,859,000
Hedged amount of foreign currency denominated loans	800,000	600,000	800,000	600,000
Visa Class B Shares [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative liabilities related to sale	4,700,000	2,200,000	4,700,000	2,200,000
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
Derivative Instruments With Accelerated Termination Provisions [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Collateral received	190,600,000	218,300,000	190,600,000	218,300,000
Securities posted collateral	28,800,000	23,400,000	28,800,000	23,400,000
Net fair value of derivative assets with adjustable posting thresholds	116,800,000	148,700,000	116,800,000	148,700,000
Net fair value of derivative liabilities with adjustable posting thresholds	23,200,000	30,000,000	23,200,000	30,000,000
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	28,100,000	50,900,000	28,100,000	50,900,000
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	14,000,000	20,700,000	14,000,000	20,700,000
Other Long-term Debt	500,000,000	500,000,000	500,000,000	500,000,000
Subordinated Debentures Subject To Mandatory Redemption Amount [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Net fair value of interest rate derivatives hedging subordinated debt	12,100,000	18,700,000	12,100,000	18,700,000
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	900,000	1,100,000	900,000	1,100,000
Additional Derivative Agreements [Member] | Derivative Instruments With Adjustable Collateral Posting Thresholds [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Collateral received	190,600,000	218,300,000	190,600,000	218,300,000
Securities posted collateral	92,300,000	102,600,000	92,300,000	102,600,000
Net fair value of derivative assets with adjustable posting thresholds	116,800,000	148,800,000	116,800,000	148,800,000
Net fair value of derivative liabilities with adjustable posting thresholds	$ 91,600,000	$ 116,500,000	$ 91,600,000	$ 116,500,000