Loans and Credit Quality (Details Textual) - Receivable [Domain] - Financing Receivable, Recorded Investment, Class of Financing Receivable [Domain]	6 Months Ended
	Jun. 30, 2014 USD ($)	Jun. 30, 2015 USD ($)	Dec. 31, 2014 USD ($)
Financing Receivable, Impaired [Line Items]
Financing Receivables, Impaired, Troubled Debt Restructuring, Write-down	$ 200,000.0
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing		$ 0	$ 0
Non-PCI nonaccrual loans		131,178,000	83,621,000
Financing Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due		33,700,000	18,800,000
Financing Receivable Recorded Investment Thirty to Eighty Nine Days Past Due		4,500,000	8,700,000
Financing Receivable Recorded Investment Nonaccrual Status Current		93,000,000	$ 56,100,000
Loans and Leases Related to the Oil and Gas Industries
Financing Receivable, Impaired [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status		$ 64,100,000
Nonperforming Financing Receivable [Member] | Loans and Leases Related to the Oil and Gas Industries
Financing Receivable, Impaired [Line Items]
Financing Receivable, Number Of Contracts		3