Borrowings (Details Textual) - USD ($)	6 Months Ended
	Jun. 30, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Interest-bearing Domestic Deposit, Brokered	$ 645,300,000	$ 636,700,000
Notes Payable, Other Payables [Member]
Debt Instrument [Line Items]
Debt Instruments Weighted Average Remaining Maturity Period	2 years 4 months 20 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	0
Unsecured Debt [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Current Borrowing Capacity	80,000,000
Unused lines of Credit [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Amount Outstanding	0	0
Federal Reserve Bank Advances [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Amount Outstanding		0
Certificate of Deposit Account Registry Service Program [Member]
Debt Instrument [Line Items]
Interest-bearing Domestic Deposit, Brokered	41,800,000	44,000,000
Federal Home Loan Bank of San Francisco [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Borrowing Capacity, Description	99,000,000
Line of Credit Facility, Amount Outstanding	0
Federal Reserve Bank Advances [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Borrowing Capacity, Description	2,000,000,000
Line of Credit Facility, Amount Outstanding	0
Loans Pledged as Collateral	2,600,000,000
Federal Home Loan Bank Advances [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Borrowing Capacity, Description	2,500,000,000
Line of Credit Facility, Amount Outstanding	$ 0	$ 380,000,000