Allowance for Loan Losses (Details Textual) - USD ($)	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Allowance For Loan And Lease Losses [Line Items]
Financing Receivable, Allowance for Credit Losses, Write-downs	$ 600,000	$ 2,200,000
Loan Commitments	6,068,239,000	6,034,870,000	$ 6,385,147,000
Minimum Non Performing Substandard Loans Outstanding for Allowance for Credit Losses	300,000
Minimum Non Performing Substandard Doubtful Loans Outstanding for Allowance for Credit Losses	100,000
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	234,000	118,000
Loans and Leases Receivable, Impaired, Interest Lost on Nonaccrual Loans	1,200,000	900,000
Total impaired loans with no related allowance
Allowance For Loan And Lease Losses [Line Items]
Loan Commitments	$ 8,300,000	$ 6,100,000	$ 7,000,000