Derivative Financial Instruments - Offsetting Assets and Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Other Assets
Gross position	$ 636	$ 7,808
Impact of master netting agreement	(636)	(7,808)
Derivative values with impact of master netting agreements (as carried on balance sheet)	0	0
Cash collateral (held) pledged	0	0
Net position	0	0
Other Liabilities
Cash collateral (held) pledged	31,300	49,100
Other Liabilities
Other Liabilities
Gross position	(8,636)	(25,937)
Impact of master netting agreement	636	7,808
Derivative values with impact of master netting agreements (as carried on balance sheet)	(8,000)	(18,129)
Cash collateral (held) pledged	31,003	48,134
Net position	$ 23,003	$ 30,005