Derivatives (Narrative) (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011	Sep. 30, 2012 Parent Company [Member]	Sep. 30, 2011 Parent Company [Member]	Sep. 30, 2012 Derivative Instruments With Accelerated Termination Provisions [Member]	Sep. 30, 2011 Derivative Instruments With Accelerated Termination Provisions [Member]	Sep. 30, 2012 Long Term Debt Hedged With Fair Value Interest Rate Derivatives Using Long Haul Method [Member]	Sep. 30, 2011 Long Term Debt Hedged With Fair Value Interest Rate Derivatives Using Long Haul Method [Member]	Oct. 31, 2012 Subordinated Debentures Subject To Mandatory Redemption Amount [Member]	Sep. 30, 2012 Subordinated Debentures Subject To Mandatory Redemption Amount [Member]	Sep. 30, 2011 Subordinated Debentures Subject To Mandatory Redemption Amount [Member]	Sep. 30, 2012 Hedge Of Held To Maturity Trust Preferred Loans [Member]	Sep. 30, 2011 Hedge Of Held To Maturity Trust Preferred Loans [Member]	Sep. 30, 2012 Additional Derivative Agreements [Member] Derivative Instruments With Adjustable Collateral Posting Thresholds [Member]	Sep. 30, 2011 Additional Derivative Agreements [Member] Derivative Instruments With Adjustable Collateral Posting Thresholds [Member]	Sep. 30, 2012 Fixed Interest Rate Swaps To Hedge [Member] Long Term Debt Hedged With Fair Value Interest Rate Derivatives Using Shortcut Method [Member] Parent Company [Member]	Sep. 30, 2011 Fixed Interest Rate Swaps To Hedge [Member] Long Term Debt Hedged With Fair Value Interest Rate Derivatives Using Shortcut Method [Member] Parent Company [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Collateral cash receivables	$ 197,400,000	$ 197,200,000	$ 197,400,000	$ 197,200,000
Collateral received								288,800,000	289,500,000								288,800,000	289,500,000
Collateral cash payables	153,300,000	168,400,000	153,300,000	168,400,000
Securities posted collateral								46,400,000	44,200,000								188,200,000	193,000,000
Net fair value of derivative assets with adjustable posting thresholds								255,800,000	266,800,000								256,300,000	269,400,000
Net fair value of derivative liabilities with adjustable posting thresholds								41,900,000	41,600,000								187,500,000	201,400,000
Total trading revenues	74,200,000	92,600,000	240,900,000	247,000,000
Certain term borrowings total										500,000,000									904,000,000	904,000,000
Net fair value of interest rate derivatives hedging long-term debt using the long-haul method										29,500,000	26,400,000		400,000	2,200,000					81,300,000	109,100,000
Noncallable senior debt maturing date			December 2015
Net fair value of interest rate derivatives hedging subordinated debt using long-haul method															3,400,000	11,100,000
Other long-term debt	2,263,238,000	2,509,804,000	2,263,238,000	2,509,804,000	2,481,660,000							200,000,000	200,000,000	200,000,000
Hedged held-to-maturity trust preferred loans principal balance						128,800,000	196,300,000
Hedged amount of foreign currency denominated loans	$ 700,000		$ 700,000