Loans and Allowance for Loan Losses - Recorded investment in nonaccrual loans by loan class (Details 4) (Loans Receivable, USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012
Recorded investment in nonaccrual loans by loan class
Nonaccrual Loans	$ 96,006	$ 109,894	$ 129,704
Balance as a percentage of unpaid principal	66.30%	69.50%	70.60%
Residential mortgage
Recorded investment in nonaccrual loans by loan class
Nonaccrual Loans	11,817	12,589	18,741
Residential construction
Recorded investment in nonaccrual loans by loan class
Nonaccrual Loans	14,592	18,702	24,341
Consumer installment
Recorded investment in nonaccrual loans by loan class
Nonaccrual Loans	389	795	908
Commercial | Commercial (secured by real estate)
Recorded investment in nonaccrual loans by loan class
Nonaccrual Loans	17,304	22,148	26,081
Commercial | Commercial & industrial
Recorded investment in nonaccrual loans by loan class
Nonaccrual Loans	29,545	31,817	36,314
Commercial | Commercial construction
Recorded investment in nonaccrual loans by loan class
Nonaccrual Loans	$ 22,359	$ 23,843	$ 23,319