Allowance for Loan Losses Allowance for Losses on Lending-Related Commitments and Impaired Loans (Summary of Impaired Loans, Including Restructured Loans) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Loans and Leases Receivable, Allowance [Abstract]
Impaired loans with an allowance for loan loss required	$ 69,487	[1]	$ 92,184	[1]
Impaired loans with no allowance for loan loss required	57,925		70,045
Total impaired loans	127,412	[2]	162,229	[2]
Allowance for loan losses related to impaired loans	6,270		8,265
Troubled debt restructurings	82,275		107,103
Reduction of interest income from non-accrual loans	2,222		3,971
Interest income recognized on impaired loans	$ 7,190		$ 8,920		$ 10,800

[1] These impaired loans require an allowance for loan losses because the estimated fair value of the loans or related collateral is less than the recorded investment in the loans.

[2] Impaired loans are considered by the Company to be non-accrual loans, TDRs or loans with principal and/or interest at risk, even if the loan is current with all payments of principal and interest.