Allowance for Loan Losses (Details Textual) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Allowance For Loan And Lease Losses [Line Items]
Provision/ (recapture) for loan losses	$ 6,391	$ 8,966	$ 14,200	$ 17,214
Loan Commitments	6,013,698	6,144,177	6,013,698	6,144,177	$ 6,385,147
Minimum Non Performing Substandard Loans Outstanding for Allowance for Credit Losses	300		300
Minimum Non Performing Substandard Doubtful Loans Outstanding for Allowance for Credit Losses	100		100
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	400	100	600	200
Loans and Leases Receivable, Impaired, Interest Lost on Nonaccrual Loans	1,400	900	2,600	1,800
Acquired Loans
Allowance For Loan And Lease Losses [Line Items]
Provision/ (recapture) for loan losses	400
Financing Receivable, Allowance for Credit Losses, Recovery			(200)
Total impaired loans with no related allowance
Allowance For Loan And Lease Losses [Line Items]
Loan Commitments	$ 200	$ 3,700	$ 200	$ 3,700	$ 7,000