Comprehensive Income/Loss (Comprised of the following Components) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ 40,695	$ 18,169
Net change in other comprehensive income (loss)	(13,538)	31,559
Ending Balance	27,157	49,728
Unrealized Gain (Loss) on Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	13,255	4,398
Net change in other comprehensive income (loss)	(7,774)	9,347
Ending Balance	5,481	13,745
Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	33,276	16,479
Net change in other comprehensive income (loss)	(6,583)	22,984
Ending Balance	26,693	39,463
Defined Benefit Postretirement Plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(5,836)	(2,708)
Net change in other comprehensive income (loss)	819	(772)
Ending Balance	(5,017)	(3,480)
AOCI Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net change in other comprehensive income (loss)	$ (13,538)	$ 31,559