Deposits (Details Textual) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Domestic Deposits, Brokered [Line Items]
Interest-bearing Domestic Deposit, Brokered	$ 863,202	$ 1,174,487
Time deposits over $250,000	355,342	413,856
Time deposits $250,000 and under	1,709,980	1,758,434
Time Deposits Balance [Domain]
Domestic Deposits, Brokered [Line Items]
Interest-bearing Domestic Deposit, Brokered	732,200	405,500
Non-maturity Deposits [Member]
Domestic Deposits, Brokered [Line Items]
Interest-bearing Domestic Deposit, Brokered	$ 800,000	$ 1,200,000