Derivative Instruments (Details 2) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Offsetting Derivative Assets
Gross amounts recognized	$ 717	$ 4,778
Gross amounts offset in the consolidated balance sheets	0	0
Net amounts presented in the consolidated balance sheets	717	4,778
Financial instruments	717	567
Financial collateral pledged	0	0
Net amounts	0	4,211
Offsetting Derivative Liabilities
Gross amounts recognized	5,303	4,893
Gross amounts offset in the consolidated balance sheets	0	0
Net amounts presented in the consolidated balance sheets	5,303	4,893
Financial instruments	717	567
Financial collateral pledged	4,357	4,326
Net amounts	$ 229	$ 0

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