Allowance for Loan Losses Allowance for Losses on Lending-Related Commitments and Impaired Loans (Narrative) (Details) (USD $)	12 Months Ended						9 Months Ended
	Dec. 31, 2014 Rate contracts		Dec. 31, 2013 contracts Rate		Dec. 31, 2012 Rate contracts		Sep. 30, 2014 contracts
Financing Receivable, Allowance for Credit Losses [Line Items]
Average recorded investment	$ 134,967,000		$ 170,658,000		$ 222,100,000
Impaired Financing Receivable, Interest Income, Accrual Method	7,190,000		8,920,000		10,800,000
Financing Receivable, Modifications, Recorded Investment	82,275,000		107,103,000
Financing Receivable, Modifications, Number of Contracts	21	[1],[2],[3]	35	[1],[2],[3]	75	[1],[2],[3]
Allowance for loan losses related to impaired loans	6,270,000		8,265,000
Financing Receivable, Modifications, Post-Modification Recorded Investment	11,967,000	[1],[2],[3]	22,680,000	[1],[2],[3]	72,512,000	[1],[2],[3]
Financing Receivables, Modifications, Weighted Average Extension Term	19 months		18 months		9 months
Weighted Average Stated Interest Rate Basis Points	1.70%		1.84%		1.57%
Financing Receivables, Modifications, Weighted Average Interest Only Term	7 months		11 months		5 months
Loan Forgiveness	0		1,000,000		800,000
Financing Receivable [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Modifications, Number of Contracts							145
Allowance for loan losses related to impaired loans	1,600,000
Loans and Leases Receivable, Impaired, Interest Income Recognized, Change in Present Value Attributable to Passage of Time	$ 724,000		$ 901,000

[1] TDRs may have more than one modification representing a concession. As such, TDRs during the period may be represented in more than one of the categories noted above.

[2] Total TDRs represent all loans restructured in TDRs during the year indicated.

[3] Balances represent the recorded investment in the loan at the time of the restructuring.