Derivative Instruments and Hedging Activities (Details 2) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES [Abstract]
Derivative Assets, Fair Value, Gross Assets	$ 41,399	$ 36,574
Gross Amount of Eligible Offsetting Recognized Derivative Liabilities	0	0
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	41,399	36,574
Derivative Asset, Not Offset, Policy Election Deduction	(15,915)	(15,050)
Cash Collateral Received	(4,515)	(7,603)
Derivative Asset, Fair Value, Amount Offset Against Collateral	20,969	13,921
Derivative Liability, Fair Value, Gross Liability	(25,829)	(22,495)
Gross Amount of Eligible Offsetting Recognized Derivative Assets	0	0
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	(25,829)	(22,495)
Derivative Liability, Not Offset, Policy Election Deduction	15,915	15,050
Cash Collateral Paid	1,004	2,716
Derivative Liability, Fair Value, Amount Offset Against Collateral	$ (8,910)	$ (4,729)