Loans and Allowance for Credit Losses Narrative (Details) (USD $)	3 Months Ended		9 Months Ended	12 Months Ended
	Sep. 30, 2011		Sep. 30, 2011	Dec. 31, 2010	Jun. 30, 2011	Mar. 31, 2011	Sep. 30, 2010	Jun. 30, 2010	Dec. 31, 2009
Accounts, Notes, Loans and Financing Receivable [Line Items]
Period for which change in loans evaluated individually for impairment			90
Loans, individually evaluated for impairment						$ 525,600,000
Loans, allowance for credit losses, individually evaluated for impairment	322,866,000		322,866,000	573,606,000		106,000,000
Period for which change in loans evaluated individually for impairment quarterly			12
Impaired loans with principal balances approximately in percentage			83.00%
Impaired loans balances, real estate as collateral	1,000,000		1,000,000
Impaired loans with primary collateral as real estate				52.00%		57.00%
Loans, collectively evaluated for impairment						11,300,000,000
Financing receivable, allowance for credit losses, collectively evaluated for impairment	11,572,789,000		11,572,789,000	11,359,701,000		164,200,000
Allowance for credit losses	268,817,000		268,817,000	275,498,000	268,633,000	271,200,000	284,874,000	280,377,000	257,553,000
Impaired loans balances allocated reserves			1,000,000
Impaired Loans without related Allowance for Loan Loss	322,866,000		322,866,000	573,606,000
Impaired Financing Receivable, Average Recorded Investment	326,623,000		390,621,000	772,300,000
Interest income on impaired loans	707,000	[1]	4,874,000	27,400,000
Commitments to lend additional funds to borrowers	169,000		169,000	1,600,000
Parent [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impaired Loans without related Allowance for Loan Loss	94,897,000		94,897,000	138,274,000
Impaired Financing Receivable, Average Recorded Investment	96,601,000		106,980,000
Interest income on impaired loans	89,000	[1]	991,000
Change in Accounting Method Accounted for as Change in Estimate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, individually evaluated for impairment						335,600,000
Loans, allowance for credit losses, individually evaluated for impairment						88,000,000
Loans, collectively evaluated for impairment						11,500,000,000
Financing receivable, allowance for credit losses, collectively evaluated for impairment						$ 182,200,000

[1] Effective April 1, 2011, all impaired loans, excluding certain accruing TDRs, were non-accrual loans. Interest income recognized for the three and nine months ended September 30, 2011 represents amounts earned on accruing TDRs.