Allowance for Loan Losses Details Textual (Details) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014	Dec. 31, 2013
Allowance For Loan And Lease Losses [Line Items]
Financing Receivable, Allowance for Credit Losses, Write-downs	$ 2,200,000
Loan Commitments	6,034,870,000	5,632,201,000	6,136,313,000
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	100,000	100,000
Loans and Leases Receivable, Impaired, Troubled Debt, Interest Income	900,000	800,000
Covered Loans
Allowance For Loan And Lease Losses [Line Items]
Loans and Leases Receivable, Allowance, Covered	41,514,000	49,970,000	40,496,000	44,027,000
Provision for Loan Losses Before Benefit Attributable to FDIC Loss Share Agreements	4,225,000	7,879,000
Benefit Attributable to FDIC Loss Share Agreements	(4,227,000)	(4,824,000)
Provision for Loan Lease and Other Losses Covered	(2,000)	3,055,000
Total impaired loans with no related allowance
Allowance For Loan And Lease Losses [Line Items]
Loan Commitments	$ 6,100,000	$ 400,000	$ 200,000