Loans and Allowance for Credit Losses Credit Quality Indicators (Details) (USD $) In Thousands	Sep. 30, 2011	Dec. 31, 2010
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	$ 11,902,097	$ 11,940,505
Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	7,547,654	7,364,712
Pass [Member] | Commercial - industrial, financial, and agricultural
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	3,204,330	3,114,482
Pass [Member] | Real-estate commercial mortage
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	3,953,387	3,776,714
Pass [Member] | Commercial - Secured [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	2,986,086	2,903,184
Pass [Member] | Commercial - Unsecured [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	218,244	211,298
Pass [Member] | Construction - Commercial Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	176,628	251,159
Pass [Member] | Construction - Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	213,309	222,357
Pass [Member] | Real-estate - construction
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	389,937	473,516
Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	442,018	661,025
Special Mention [Member] | Commercial - industrial, financial, and agricultural
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	179,410	259,104
Special Mention [Member] | Real-estate commercial mortage
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	214,970	306,926
Special Mention [Member] | Commercial - Secured [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	175,459	244,927
Special Mention [Member] | Commercial - Unsecured [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	3,951	14,177
Special Mention [Member] | Construction - Commercial Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	39,947	84,774
Special Mention [Member] | Construction - Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	7,691	10,221
Special Mention [Member] | Real-estate - construction
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	47,638	94,995
Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	785,646	791,963
Substandard [Member] | Commercial - industrial, financial, and agricultural
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	306,424	330,798
Substandard [Member] | Real-estate commercial mortage
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	322,798	292,340
Substandard [Member] | Commercial - Secured [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	295,096	323,187
Substandard [Member] | Commercial - Unsecured [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	11,328	7,611
Substandard [Member] | Construction - Commercial Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	143,791	156,966
Substandard [Member] | Construction - Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	12,633	11,859
Substandard [Member] | Real-estate - construction
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	156,424	168,825
Commercial - industrial, financial, and agricultural
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	3,690,164	3,704,384
Real-estate commercial mortage
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	4,491,155	4,375,980
Commercial - Secured [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	3,456,641	3,471,298
Commercial - Unsecured [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	233,523	233,086
Construction - Commercial Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	360,366	492,899
Construction - Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	233,633	244,437
Real-estate - construction
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	593,999	737,336
Commercial Loans, Commerical Mortgages, Constructions Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	$ 8,775,318	$ 8,817,700