Derivative Financial Instruments (Details 4) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Offsetting Liabilities
Gross Amounts of Recognized Liabilities	$ 155,124	$ 169,716
Gross Amounts Offset in the Statement of Financial Condition	27	60
Net Amounts Offset in the Statement of Financial Condition	155,097	169,656
Gross Amounts Not Offset in the Statement of Financial Condition
Financial Instruments	149,835	162,913
Cash Collateral Pledge	2,705	3,794
Net Amount	2,557	2,949
Interest rate swap contracts
Offsetting Liabilities
Gross Amounts of Recognized Liabilities	5,289	6,803
Gross Amounts Offset in the Statement of Financial Condition	27	60
Net Amounts Offset in the Statement of Financial Condition	5,262	6,743
Gross Amounts Not Offset in the Statement of Financial Condition
Cash Collateral Pledge	2,705	3,794
Net Amount	2,557	2,949
Repurchase agreements
Offsetting Liabilities
Gross Amounts of Recognized Liabilities	149,835	162,913
Gross Amounts Offset in the Statement of Financial Condition	0	0
Net Amounts Offset in the Statement of Financial Condition	149,835	162,913
Gross Amounts Not Offset in the Statement of Financial Condition
Financial Instruments	149,835	162,913
Net Amount	$ 0	$ 0