Loans and leases and the allowance for credit losses (Details 8) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Recorded investment in loans and leases on the basis of the Company's impairment methodology
Loans and leases, net of unearned discount	$ 62,851,272	$ 60,096,005
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	16,395,587	15,734,436
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	24,898,707	24,411,114
Residential real estate [Member]
Recorded investment in loans and leases on the basis of the Company's impairment methodology
Loans and leases, net of unearned discount	9,811,525	7,923,165
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	11,745,453	12,027,290
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	1,035,198	1,110,873
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	161,669	171,442
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	504,281	561,615
Individually evaluated for impairment [Member] | Residential real estate [Member]
Recorded investment in loans and leases on the basis of the Company's impairment methodology
Loans and leases, net of unearned discount	295,314	306,320
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	73,934	71,496
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	61,255,374	58,331,770
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	16,217,494	15,539,232
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	23,901,962	23,281,585
Collectively Evaluated For Impairment [Member] | Residential real estate [Member]
Recorded investment in loans and leases on the basis of the Company's impairment methodology
Loans and leases, net of unearned discount	9,469,076	7,560,104
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	11,666,842	11,950,849
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	560,700	653,362
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	16,424	23,762
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	492,464	567,914
Purchased Impaired [Member] | Residential real estate [Member]
Recorded investment in loans and leases on the basis of the Company's impairment methodology
Loans and leases, net of unearned discount	47,135	56,741
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	$ 4,677	$ 4,945