Balance Sheet Offsetting (Details) - June 30, 2018 - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Offsetting Derivative Assets [Abstract]
Gross amounts recognized	$ 68,065	$ 29,503
Gross amounts offset in the balance sheet	0	0
Net amounts presented in the balance sheet	68,065	29,503
Financial instruments	(27,040)	(16,140)
Collateral	(38,601)	(13,234)
Net amount	2,424	129
Offsetting Derivative Liabilities [Abstract]
Gross amounts recognized	63,363	37,164
Gross amounts offset in the balance sheet	0	0
Net amounts presented in the balance sheet	63,363	37,164
Financial instruments	(27,040)	(16,140)
Collateral	(35,513)	(20,662)
Net amount	$ 810	$ 362

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