Loans and Allowance for Credit Losses Credit Quality Indicators (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	$ 11,975,964	$ 11,940,505
Commercial - industrial, financial, and agricultural
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	3,639,368	3,704,384
Real-estate commercial mortage
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	4,602,596	4,375,980
Commercial - Secured [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	3,393,559	3,471,298
Commercial - Unsecured [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	245,809	233,086
Construction - Commercial Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	352,938	492,899
Construction - Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	209,380	244,437
Real-estate - construction
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	562,318	737,336
Commercial Loans, Commerical Mortgages, Constructions Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	8,804,282	8,817,700
Loans and Leases Receivable, Ratio of Nonperforming Loans to All Loans	100.00%	100.00%
Pass [Member] | Commercial - industrial, financial, and agricultural
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	3,208,919	3,114,482
Pass [Member] | Real-estate commercial mortage
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	4,099,103	3,776,714
Pass [Member] | Commercial - Secured [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	2,977,957	2,903,184
Pass [Member] | Commercial - Unsecured [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	230,962	211,298
Pass [Member] | Construction - Commercial Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	175,706	251,159
Pass [Member] | Construction - Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	186,049	222,357
Pass [Member] | Real-estate - construction
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	361,755	473,516
Pass [Member] | Commercial Loans, Commerical Mortgages, Constructions Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	7,669,777	7,364,712
Loans and Leases Receivable, Ratio of Nonperforming Loans to All Loans	87.10%	83.50%
Special Mention [Member] | Commercial - industrial, financial, and agricultural
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	172,654	259,104
Special Mention [Member] | Real-estate commercial mortage
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	160,935	306,926
Special Mention [Member] | Commercial - Secured [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	166,588	244,927
Special Mention [Member] | Commercial - Unsecured [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	6,066	14,177
Special Mention [Member] | Construction - Commercial Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	50,854	84,774
Special Mention [Member] | Construction - Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	7,022	10,221
Special Mention [Member] | Real-estate - construction
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	57,876	94,995
Special Mention [Member] | Commercial Loans, Commerical Mortgages, Constructions Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	391,465	661,025
Loans and Leases Receivable, Ratio of Nonperforming Loans to All Loans	4.50%	7.50%
Substandard [Member] | Commercial - industrial, financial, and agricultural
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	257,795	330,798
Substandard [Member] | Real-estate commercial mortage
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	342,558	292,340
Substandard [Member] | Commercial - Secured [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	249,014	323,187
Substandard [Member] | Commercial - Unsecured [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	8,781	7,611
Substandard [Member] | Construction - Commercial Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	126,378	156,966
Substandard [Member] | Construction - Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	16,309	11,859
Substandard [Member] | Real-estate - construction
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	142,687	168,825
Substandard [Member] | Commercial Loans, Commerical Mortgages, Constructions Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	$ 743,040	$ 791,963
Loans and Leases Receivable, Ratio of Nonperforming Loans to All Loans	8.40%	9.00%