Loans and leases and the allowance for credit losses (Details 6) (USD $) In Thousands	Sep. 30, 2011	Dec. 31, 2010
Summary of Loan grades
Loans and leases, net of unearned discount	$ 58,401,264	$ 51,990,382
Commercial, financial, leasing [Member] | Pass [Member]
Summary of Loan grades
Loans and leases, net of unearned discount	14,350,581	12,384,512
Pass [Member] | Commercial Real Estate Excluding Residential Builder and Developer and Other Construction [Member]
Summary of Loan grades
Loans and leases, net of unearned discount	18,851,277	15,855,774
Pass [Member] | Residential builder and developer [Member]
Summary of Loan grades
Loans and leases, net of unearned discount	412,916	722,747
Pass [Member] | Other commercial construction [Member]
Summary of Loan grades
Loans and leases, net of unearned discount	2,600,236	2,263,965
Commercial, financial, leasing [Member] | Criticized Accrual [Member]
Summary of Loan grades
Loans and leases, net of unearned discount	717,219	832,733
Criticized Accrual [Member] | Commercial Real Estate Excluding Residential Builder and Developer and Other Construction [Member]
Summary of Loan grades
Loans and leases, net of unearned discount	401,825	891,655
Criticized Accrual [Member] | Residential builder and developer [Member]
Summary of Loan grades
Loans and leases, net of unearned discount	938,076	311,932
Criticized Accrual [Member] | Other commercial construction [Member]
Summary of Loan grades
Loans and leases, net of unearned discount	150,171	519,651
Commercial, financial, leasing [Member] | Criticized Nonaccrual [Member]
Summary of Loan grades
Loans and leases, net of unearned discount	150,702	173,365
Criticized Nonaccrual [Member] | Commercial Real Estate Excluding Residential Builder and Developer and Other Construction [Member]
Summary of Loan grades
Loans and leases, net of unearned discount	182,953	184,361
Criticized Nonaccrual [Member] | Residential builder and developer [Member]
Summary of Loan grades
Loans and leases, net of unearned discount	318,957	316,811
Criticized Nonaccrual [Member] | Other commercial construction [Member]
Summary of Loan grades
Loans and leases, net of unearned discount	104,895	116,265
Commercial, financial, leasing [Member]
Summary of Loan grades
Loans and leases, net of unearned discount	15,218,502	13,390,610
Commercial Real Estate Excluding Residential Builder and Developer and Other Construction [Member]
Summary of Loan grades
Loans and leases, net of unearned discount	19,436,055	16,931,790
Residential builder and developer [Member]
Summary of Loan grades
Loans and leases, net of unearned discount	1,669,949	1,351,490
Other commercial construction [Member]
Summary of Loan grades
Loans and leases, net of unearned discount	$ 2,855,302	$ 2,899,881