Borrowings (Details Textual) (USD $)	3 Months Ended
	Mar. 31, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Interest-bearing Domestic Deposit, Brokered	$ 814,900,000	$ 636,700,000
Brokered Deposits For The Quarter	178,200,000
Notes Payable, Other Payables [Member]
Debt Instrument [Line Items]
Debt Instruments Weighted Average Remaining Maturity Period	2 years 5 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
Federal Reserve Bank Advances [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Amount Outstanding		0
Federal Home Loan Bank Advances [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Amount Outstanding	615,000,000	380,000,000
Line of Credit Facility, Current Borrowing Capacity	2,400,000,000
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
Certificate of Deposit Account Registry Service Program [Member]
Debt Instrument [Line Items]
Interest-bearing Domestic Deposit, Brokered	46,500,000	44,000,000
Federal Home Loan Bank of San Francisco [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Borrowing Capacity, Description	1,500,000,000
Line of Credit Facility, Amount Outstanding	0
Loans Pledged as Collateral	$ 2,100,000,000