Loans and Allowance for Loan Losses (Narrative) (Details) (USD $)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	$ 991,086,000		$ 1,012,405,000		$ 1,193,641,000
Accruing troubled debt restructuring	635,100,000	687,400,000	635,100,000	687,400,000	673,400,000
Provision for losses on loans	13,077,000	44,222,000	48,773,000	110,271,000
Interest income recognized	5,356,000		10,819,000		22,865,000
Interest income recognized for accruing TDRs			10,800,000
Substandard [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	991,100,000		1,010,000,000
Retail loan substandard period (in days)			90
Loss And Charged Off [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retail loan charge-off period (in days)			120
Accruing TDRs With Modifications And Renewals Completed [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision for losses on loans			39,300,000		41,400,000
Minimum [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial-type impaired loans				1,000,000
With No Related Allowance Recorded [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	133,888,000		139,808,000		373,750,000
Interest income recognized	$ 0		$ 0	$ 0	$ 0