Fair Value Measurements (Details 3) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2011	Dec. 31, 2010
Financial assets:
Cash and cash equivalents	$ 1,422,831	$ 1,452,397	$ 1,332,915	$ 933,755
Interest-bearing deposits at banks	1,069,717	154,960
Trading account assets	544,938	561,834
Investment securities	7,057,300	7,673,154
Loans and leases:
Allowance for credit losses	(917,028)	(908,290)
Loans and leases, net	61,934,244	59,187,715
Financial liabilities:
Noninterest-bearing Deposit Liabilities, Domestic	(22,854,794)	(20,017,883)
Time deposits	(5,330,239)	(6,107,530)
Deposits, Foreign	(366,164)	(355,927)
Long-term borrowings	(5,687,868)	(6,686,226)
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Financial assets:
Cash and cash equivalents	1,343,415
Trading account assets	53,472
Investment securities	108,172
Loans and leases:
Allowance for credit losses
Significant Observable Inputs (Level 2) [Member]
Financial assets:
Cash and cash equivalents	79,416
Interest-bearing deposits at banks	1,069,717
Trading account assets	491,466
Investment securities	5,598,494
Loans and leases:
Commercial real estate loans	109,645
Residential real estate loans	6,617,925
Allowance for credit losses
Loans and leases, net	6,727,570
Accrued interest receivable	220,510
Financial liabilities:
Noninterest-bearing Deposit Liabilities, Domestic	(22,854,794)
Savings Deposits And Now Accounts	(33,997,610)
Time deposits	(5,360,561)
Deposits, Foreign	(366,164)
Federal Funds Purchased and Short Term Borrowings	(975,575)
Long-term borrowings	(5,784,700)
Interest Payable	(67,523)
Trading Liabilities	(430,101)
Other financial instruments:
Gain loss on commitments to sell real estate loans	(12,857)
Interest rate swap agreements used for interest rate risk management	149,947
Significant Unobservable Inputs (Level 3) [Member]
Financial assets:
Investment securities	1,294,005
Loans and leases:
Commercial loans and leases	16,146,408
Commercial real estate loans	24,577,798
Residential real estate loans	3,225,496
Consumer loans	11,605,448
Allowance for credit losses
Loans and leases, net	55,555,150
Other financial instruments:
Commitments to originate real estate loans for sale	34,051
Other credit related commitments	(127,616)
Carrying Amount [Member]
Financial assets:
Cash and cash equivalents	1,422,831	1,452,397
Interest-bearing deposits at banks	1,069,717	154,960
Trading account assets	544,938	561,834
Investment securities	7,057,300	7,673,154
Loans and leases:
Commercial loans and leases	16,395,587	15,734,436
Commercial real estate loans	24,898,707	24,411,114
Residential real estate loans	9,811,525	7,923,165
Consumer loans	11,745,453	12,027,290
Allowance for credit losses	(917,028)	(908,290)
Loans and leases, net	61,934,244	59,187,715
Accrued interest receivable	220,510	222,618
Financial liabilities:
Noninterest-bearing Deposit Liabilities, Domestic	(22,854,794)	(20,017,883)
Savings Deposits And Now Accounts	(33,997,610)	(32,913,309)
Time deposits	(5,330,239)	(6,107,530)
Deposits, Foreign	(366,164)	(355,927)
Federal Funds Purchased and Short Term Borrowings	(975,575)	(782,082)
Long-term borrowings	(5,687,868)	(6,686,226)
Interest Payable	(67,523)	(67,900)
Trading Liabilities	(430,101)	(434,559)
Other financial instruments:
Commitments to originate real estate loans for sale	34,051	6,923
Gain loss on commitments to sell real estate loans	(12,857)	(3,498)
Other credit related commitments	(127,616)	(109,828)
Interest rate swap agreements used for interest rate risk management	149,947	147,302
Estimated fair value [Member]
Financial assets:
Cash and cash equivalents	1,422,831	1,452,397
Interest-bearing deposits at banks	1,069,717	154,960
Trading account assets	544,938	561,834
Investment securities	7,000,671	7,608,008
Loans and leases:
Commercial loans and leases	16,146,408	15,507,342
Commercial real estate loans	24,687,443	24,024,585
Residential real estate loans	9,843,421	7,782,935
Consumer loans	11,605,448	11,869,813
Allowance for credit losses
Loans and leases, net	62,282,720	59,184,675
Accrued interest receivable	220,510	222,618
Financial liabilities:
Noninterest-bearing Deposit Liabilities, Domestic	(22,854,794)	(20,017,883)
Savings Deposits And Now Accounts	(33,997,610)	(32,913,309)
Time deposits	(5,360,561)	(6,133,806)
Deposits, Foreign	(366,164)	(355,927)
Federal Funds Purchased and Short Term Borrowings	(975,575)	(782,082)
Long-term borrowings	(5,784,700)	(6,720,174)
Interest Payable	(67,523)	(67,900)
Trading Liabilities	(430,101)	(434,559)
Other financial instruments:
Commitments to originate real estate loans for sale	34,051	6,923
Gain loss on commitments to sell real estate loans	(12,857)	(3,498)
Other credit related commitments	(127,616)	(109,828)
Interest rate swap agreements used for interest rate risk management	$ 149,947	$ 147,302