Loans and Allowance for Credit Losses Loans Modified Under Troubled Debt Restructurings (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Financing Receivable, Modifications [Line Items]
Total accruing TDRs	$ 76,795	$ 66,175
Non-accrual TDRs	32,411	32,587
Total TDRs	109,206	98,762
Real-estate - residential mortgage [Member]
Financing Receivable, Modifications [Line Items]
Total accruing TDRs	33,800	32,331
Real-estate commercial mortage [Member]
Financing Receivable, Modifications [Line Items]
Total accruing TDRs	28,153	22,425
Real-estate - construction
Financing Receivable, Modifications [Line Items]
Total accruing TDRs	10,303	7,645
Commercial - industrial, financial, and agricultural
Financing Receivable, Modifications [Line Items]
Total accruing TDRs	4,075	3,581
Consumer and Home Equity [Member]
Financing Receivable, Modifications [Line Items]
Total accruing TDRs	$ 464	$ 193