Loans and leases and the allowance for credit losses (Details 6) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Summary of Loan grades
Loans and leases, net of unearned discount	$ 62,851,272	$ 60,096,005
Commercial, financial, leasing [Member]
Summary of Loan grades
Loans and leases, net of unearned discount	16,395,587	15,734,436
Commercial Real Estate Excluding Residential Builder and Developer and Other Construction [Member]
Summary of Loan grades
Loans and leases, net of unearned discount	21,380,406	20,259,448
Residential builder and developer [Member]
Summary of Loan grades
Loans and leases, net of unearned discount	1,333,674	1,508,333
Other commercial construction [Member]
Summary of Loan grades
Loans and leases, net of unearned discount	2,184,627	2,643,333
Pass [Member] | Commercial, financial, leasing [Member]
Summary of Loan grades
Loans and leases, net of unearned discount	15,499,951	14,869,636
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	20,403,488	19,089,252
Pass [Member] | Residential builder and developer [Member]
Summary of Loan grades
Loans and leases, net of unearned discount	989,903	1,085,970
Pass [Member] | Other commercial construction [Member]
Summary of Loan grades
Loans and leases, net of unearned discount	1,903,981	2,254,609
Criticized Accrual [Member] | Commercial, financial, leasing [Member]
Summary of Loan grades
Loans and leases, net of unearned discount	742,080	701,202
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	803,640	999,085
Criticized Accrual [Member] | Residential builder and developer [Member]
Summary of Loan grades
Loans and leases, net of unearned discount	103,523	140,787
Criticized Accrual [Member] | Other commercial construction [Member]
Summary of Loan grades
Loans and leases, net of unearned discount	254,343	282,399
Criticized Nonaccrual [Member] | Commercial, financial, leasing [Member]
Summary of Loan grades
Loans and leases, net of unearned discount	153,556	163,598
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	173,278	171,111
Criticized Nonaccrual [Member] | Residential builder and developer [Member]
Summary of Loan grades
Loans and leases, net of unearned discount	240,248	281,576
Criticized Nonaccrual [Member] | Other commercial construction [Member]
Summary of Loan grades
Loans and leases, net of unearned discount	$ 26,303	$ 106,325