Loans and Allowance for Loan Losses (Narrative) (Details) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase in allocated allowance			$ 23,000,000
Average recorded investment in impaired loans	537,540,000	881,953,000	537,540,000	881,953,000
Interest income recognized	3,731,000		11,711,000	0	21,114,000
Average recorded investment in impaired loans	559,676,000		666,840,000		952,318,000
Interest income recognized for accruing TDRs	3,700,000	5,200,000	11,700,000	16,100,000
Accruing troubled debt restructuring	408,700,000		408,700,000		574,200,000
Allowance for loan losses	269,376,000	318,612,000	269,376,000	318,612,000	307,560,000	277,783,000	334,880,000	373,405,000
Substandard [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retail loan substandard period (in days)			90 days
Loss and Charged Off [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retail loans downgraded to loss (in days)			120 days
Accruing TDRs With Modifications And Renewals Completed [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accruing troubled debt restructuring	408,700,000		408,700,000		556,400,000
Allowance for loan losses	22,700,000		22,700,000		27,700,000
Minimum [Member] | Accruing TDRs With Modifications And Renewals Completed [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial-type impaired loans			$ 1,000,000