Loans And Allowance For Credit Losses (Narrative) (Details) (USD $)	3 Months Ended			9 Months Ended		12 Months Ended
	Sep. 30, 2012 M	Sep. 30, 2011	Mar. 31, 2011	Sep. 30, 2012 Y Grades M Payments Billing_Cycles D	Sep. 30, 2011	Sep. 30, 2012	Dec. 31, 2011
Loans And Allowance For Credit Losses [Line Items]
Unearned income and fees, net of related costs	$ 131,000,000			$ 131,000,000		$ 131,000,000	$ 133,100,000
Owner occupied and commercial real estate loans, unamortized premiums	61,400,000			61,400,000		61,400,000	73,400,000
Loans at carrying value pledged as collateral for current and potential borrowings	20,100,000,000			20,100,000,000		20,100,000,000	21,100,000,000
Principle amount of loans held for sale sold	369,000,000	353,000,000		1,244,000,000	1,202,000,000
Increase in loans held for sale	452,000,000	336,000,000		1,260,000,000	1,124,000,000
Income from loans sold, excluding servicing	8,500,000	3,800,000		22,400,000	13,900,000
Number of days for consumer loans to be charged off				180
Number of days for closed-end loans to be charged off				120
Period of loss migration analysis, maximum months	60
Minimum number of days past due for nonaccrual status				90
Minimum number of monthly payments in arrears when reporting past due				2
Minimum number of billing cycles in arrears when reported as past due				2
Minimum number of days unpaid when reported as past due				30
Maximum loan amount for internally assigned loan grades				500,000
Number of probability of default grades				14
Number of loss given default grades				12
Threshold for nonaccrual loans for evaluation of impairment				1,000,000
Minimum number of months for borrower to meet terms For TDR status				6
Unused commitments to extend credit on TDR loans	17,000,000			17,000,000		17,000,000	9,000,000
Recorded investment in TDR loans modified with interest rates below market	210,100,000			210,100,000		210,100,000	269,900,000
Loans modified as troubled debt restructuring loans						164,600,000
Remittance by FDIC recognized in other noninterest income			18,900,000
Acquired foreclosed assets and subsequent real estate foreclosures	11,800,000			11,800,000		11,800,000	24,300,000
Net carrying amount of certain PCI loans	40,100,000			40,100,000		40,100,000	42,600,000
Increase (decrease) on gross provision for loan losses	(9,000,000)	(600,000)		(16,300,000)	(300,000)
Charge-offs (recoveries), net before FDIC indemnification	(1,400,000)	900,000		(8,100,000)	11,400,000
Total reversal amount to ALLL	8,300,000	3,500,000		18,900,000	12,600,000
Additional interest income due to increased cash flows from acquired loans	17,600,000	15,400,000		45,500,000	43,500,000
Additional noninterest expense due to increased cash flows from acquired loans	14,400,000	20,600,000		35,600,000	61,300,000
Loss sharing reimbursement, minimum	80.00%			80.00%		80.00%
Loss sharing reimbursement, maximum	95.00%			95.00%		95.00%
Maximum Number of Years For FDIC Coverage For All Except Single Family Residential Loans				5
Maximum Number Of Years For FDIC Coverage For Single Family Residential Loans				10
Increase in allowance for loan and leases due to change in methodology	$ 19,000,000
Commercial [Member]
Loans And Allowance For Credit Losses [Line Items]
Subsequent payment default period, number of days				90
Consumer [Member]
Loans And Allowance For Credit Losses [Line Items]
Subsequent payment default period, number of days				60