Loans and Allowance for Credit Losses Present Loans, Net of Unearned Income and Their Related Allowance for Loan Losses, by Portfolio Segment (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011		Mar. 31, 2011	Dec. 31, 2010		Dec. 31, 2009
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment			$ 164,200
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment			106,000
Loans and Leases Receivable, Allowance	256,471			274,271		256,698
Loans and Leases Receivable, Net of Deferred Income	11,968,970			11,933,307
Unallocated allowance	10.00%			15.00%
Real-estate commercial mortage
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	4,476,262			4,217,660
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	126,334			158,320
Loans and Leases Receivable, Allowance	85,112			40,831
Loans and Leases Receivable, Net of Deferred Income	4,602,596			4,375,980
Real-estate commercial mortage | Allowance for Loan and Lease Losses [Member]
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	49,052			22,836
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	36,060			17,995
Loans and Leases Receivable, Allowance	85,112			40,831
Commercial - industrial, financial, and agricultural
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	3,560,487			3,469,775
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	78,881			234,609
Loans and Leases Receivable, Allowance	74,896			101,436
Loans and Leases Receivable, Net of Deferred Income	3,639,368			3,704,384
Commercial - industrial, financial, and agricultural | Allowance for Loan and Lease Losses [Member]
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	46,471			32,323
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	28,425			69,113
Loans and Leases Receivable, Allowance	74,896			101,436
Real-estate - home equity
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	1,619,069			1,641,777
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	5,493			0
Loans and Leases Receivable, Allowance	12,841			6,454
Loans and Leases Receivable, Net of Deferred Income	1,624,562			1,641,777
Real-estate - home equity | Allowance for Loan and Lease Losses [Member]
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	9,765			6,454
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	3,076			0
Loans and Leases Receivable, Allowance	12,841			6,454
Real-estate - residential mortgage
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	1,057,274			956,260
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	39,918			39,730
Loans and Leases Receivable, Allowance	22,986			17,425
Loans and Leases Receivable, Net of Deferred Income	1,097,192			995,990
Real-estate - residential mortgage | Allowance for Loan and Lease Losses [Member]
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	6,691			11,475
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	16,295			5,950
Loans and Leases Receivable, Allowance	22,986			17,425
Real-estate - construction
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	553,106			660,238
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	62,339			140,947
Loans and Leases Receivable, Allowance	30,066			58,117
Loans and Leases Receivable, Net of Deferred Income	615,445			801,185
Real-estate - construction | Allowance for Loan and Lease Losses [Member]
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	17,610			35,247
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	12,456			22,870
Loans and Leases Receivable, Allowance	30,066			58,117
Consumer
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	317,733			350,161
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	368			0
Loans and Leases Receivable, Allowance	2,083			4,669
Loans and Leases Receivable, Net of Deferred Income	318,101			350,161
Consumer | Allowance for Loan and Lease Losses [Member]
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	1,855			4,669
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	228			0
Loans and Leases Receivable, Allowance	2,083			4,669
Leasing and Other and Overdrafts [Member]
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	71,650			63,830
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	56			0
Loans and Leases Receivable, Allowance	2,397			3,840
Loans and Leases Receivable, Net of Deferred Income	71,706			63,830
Leasing and Other and Overdrafts [Member] | Allowance for Loan and Lease Losses [Member]
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	2,360			3,840
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	37			0
Loans and Leases Receivable, Allowance	2,397			3,840
Unallocated
Loans and Leases Receivable, Allowance	26,090	[1]		41,499	[1]
Unallocated | Allowance for Loan and Lease Losses [Member]
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	26,090	[1]		41,499	[1]
Loans and Leases Receivable, Allowance	$ 26,090	[1]		$ 41,499	[1]

[1] The Corporation’s unallocated allowance, which was approximately 10% and 15% as of December 31, 2011 and December 31, 2010, respectively, was reasonable and appropriate as the estimates used in the allocation process are inherently imprecise.