Borrowings and Subordinated Debentures (Details Textual) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Debt Instrument [Line Items]
Interest-bearing Domestic Deposit, Brokered	636,700,000	$ 49,400,000
Federal Reserve Bank Advances [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Amount Outstanding		0
Notes Payable, Other Payables [Member]
Debt Instrument [Line Items]
Debt Instruments Weighted Average Remaining Maturity Period	2 years 3 months 18 days
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Borrowing Capacity, Description	75,000,000
Line of Credit Facility, Amount Outstanding	0
Federal Home Loan Bank Advances [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Current Borrowing Capacity	2,400,000,000
Line of Credit Facility, Amount Outstanding	380,000,000	106,600,000
Unsecured Debt [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Borrowing Capacity, Description	80,000,000
Unused lines of Credit [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Amount Outstanding	0	0
Certificate of Deposit Account Registry Service Program [Member]
Debt Instrument [Line Items]
Interest-bearing Domestic Deposit, Brokered	44,000,000	49,400,000
Federal Home Loan Bank of San Francisco [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Borrowing Capacity, Description	1,300,000,000
Loans Pledged as Collateral	1,800,000,000
Line of Credit Facility, Amount Outstanding	0