Loans and leases and the allowance for credit losses (Details 8) (USD $) In Thousands	Sep. 30, 2011	Dec. 31, 2010
Recorded investment in loans and leases on the basis of the Company's impairment methodology
Loans and leases, net of unearned discount	$ 58,401,264	$ 51,990,382
Commercial, financial, leasing, etc. [Member]
Recorded investment in loans and leases on the basis of the Company's impairment methodology
Loans and leases, net of unearned discount	15,218,502	13,390,610
Commercial, financial, leasing, etc. [Member] | Individually evaluated for impairment [Member]
Recorded investment in loans and leases on the basis of the Company's impairment methodology
Loans and leases, net of unearned discount	159,287	173,365
Commercial, financial, leasing, etc. [Member] | Collectively Evaluated For Impairment [Member]
Recorded investment in loans and leases on the basis of the Company's impairment methodology
Loans and leases, net of unearned discount	15,033,423	13,214,995
Commercial, financial, leasing, etc. [Member] | Purchased Impaired [Member]
Recorded investment in loans and leases on the basis of the Company's impairment methodology
Loans and leases, net of unearned discount	25,792	2,250
Commercial real estate loans [Member]
Recorded investment in loans and leases on the basis of the Company's impairment methodology
Loans and leases, net of unearned discount	23,961,306	21,183,161
Commercial real estate loans [Member] | Individually evaluated for impairment [Member]
Recorded investment in loans and leases on the basis of the Company's impairment methodology
Loans and leases, net of unearned discount	611,034	617,437
Commercial real estate loans [Member] | Collectively Evaluated For Impairment [Member]
Recorded investment in loans and leases on the basis of the Company's impairment methodology
Loans and leases, net of unearned discount	22,737,522	20,482,641
Commercial real estate loans [Member] | Purchased Impaired [Member]
Recorded investment in loans and leases on the basis of the Company's impairment methodology
Loans and leases, net of unearned discount	612,750	83,083
Residential real estate loans [Member]
Recorded investment in loans and leases on the basis of the Company's impairment methodology
Loans and leases, net of unearned discount	7,065,451	5,928,056
Residential real estate loans [Member] | Individually evaluated for impairment [Member]
Recorded investment in loans and leases on the basis of the Company's impairment methodology
Loans and leases, net of unearned discount	287,510	286,612
Residential real estate loans [Member] | Collectively Evaluated For Impairment [Member]
Recorded investment in loans and leases on the basis of the Company's impairment methodology
Loans and leases, net of unearned discount	6,718,821	5,632,124
Residential real estate loans [Member] | Purchased Impaired [Member]
Recorded investment in loans and leases on the basis of the Company's impairment methodology
Loans and leases, net of unearned discount	59,120	9,320
Consumer loans [Member]
Recorded investment in loans and leases on the basis of the Company's impairment methodology
Loans and leases, net of unearned discount	12,156,005	11,488,555
Consumer loans [Member] | Individually evaluated for impairment [Member]
Recorded investment in loans and leases on the basis of the Company's impairment methodology
Loans and leases, net of unearned discount	71,866	72,082
Consumer loans [Member] | Collectively Evaluated For Impairment [Member]
Recorded investment in loans and leases on the basis of the Company's impairment methodology
Loans and leases, net of unearned discount	12,078,169	11,414,107
Consumer loans [Member] | Purchased Impaired [Member]
Recorded investment in loans and leases on the basis of the Company's impairment methodology
Loans and leases, net of unearned discount	5,970	2,366
Individually evaluated for impairment [Member]
Recorded investment in loans and leases on the basis of the Company's impairment methodology
Loans and leases, net of unearned discount	1,129,697	1,149,496
Collectively Evaluated For Impairment [Member]
Recorded investment in loans and leases on the basis of the Company's impairment methodology
Loans and leases, net of unearned discount	56,567,935	50,743,867
Purchased Impaired [Member]
Recorded investment in loans and leases on the basis of the Company's impairment methodology
Loans and leases, net of unearned discount	$ 703,632	$ 97,019