Loans and leases and the allowance for credit losses (Details 7) (USD $) In Thousands	Jun. 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	$ 58,541,229	$ 51,990,382
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	1,252,413	1,227,553
Individually evaluated for impairment [Member] | Commercial, financial, leasing [Member]
Recorded investment in loans and leases on the basis of the Company's impairment methodology
Loans and leases, net of unearned discount	169,797	186,739
Individually evaluated for impairment [Member] | 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	717,317	682,120
Individually evaluated for impairment [Member] | 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	293,257	286,612
Individually evaluated for impairment [Member] | 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	72,042	72,082
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	56,535,838	50,665,810
Collectively evaluated for impairment [Member] | Commercial, financial, leasing [Member]
Recorded investment in loans and leases on the basis of the Company's impairment methodology
Loans and leases, net of unearned discount	14,833,322	13,201,621
Collectively evaluated for impairment [Member] | 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	22,902,012	20,417,958
Collectively evaluated for impairment [Member] | 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	6,613,337	5,632,124
Collectively evaluated for impairment [Member] | 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	12,187,167	11,414,107
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	752,978	97,019
Purchased Impaired [Member] | Commercial, financial, leasing [Member]
Recorded investment in loans and leases on the basis of the Company's impairment methodology
Loans and leases, net of unearned discount	37,773	2,250
Purchased Impaired [Member] | 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	644,397	83,083
Purchased Impaired [Member] | 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	64,327	9,320
Purchased Impaired [Member] | 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	6,481	2,366
Commercial, financial, leasing [Member]
Recorded investment in loans and leases on the basis of the Company's impairment methodology
Loans and leases, net of unearned discount	15,040,892	13,390,610
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	24,263,726	21,183,161
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	6,970,921	5,928,056
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	$ 12,265,690	$ 11,488,555