Derivative Financial Instruments - Offsetting Assets and Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Other Assets
Gross position	$ 794	$ 812
Impact of master netting agreement	(794)	(812)
Derivative values with impact of master netting agreements (as carried on balance sheet)	0	0
Cash collateral pledged	0	0
Net position	0	0
Other Liabilities
Cash collateral pledged	31,600	21,600
Other Liabilities
Other Liabilities
Gross position	(1,089)	(2,584)
Impact of master netting agreement	794	812
Derivative values with impact of master netting agreements (as carried on balance sheet)	(295)	(1,772)
Cash collateral pledged	31,637	21,586
Net position	$ 31,342	$ 19,814