Derivative Instruments - Offsetting Derivatives (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Offsetting Derivative Assets
Gross amounts recognized	$ 1,620	$ 717
Gross amounts offset in the consolidated balance sheets	0	0
Net amounts presented in the consolidated balance sheets	1,620	717
Financial instruments	1,620	717
Financial collateral pledged	0	0
Net amounts	0	0
Offsetting Derivative Liabilities
Gross amounts recognized	6,768	5,303
Gross amounts offset in the consolidated balance sheets	0	0
Net amounts presented in the consolidated balance sheets	6,768	5,303
Financial instruments	1,620	717
Financial collateral pledged	2,745	4,357
Net amounts	$ 2,403	$ 229

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