Accumulated Other Comprehensive Income (Changes in AOCI by Component) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	$ 181,077	$ 47,150	$ 40,367	$ (35,305)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(1,504)	17,730	141,640	101,699
Reclassification from Accumulated Other Comprehensive Income (Loss), Current Period, Net of Tax	(1,972)	4	(4,406)	(1,510)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent, Total	(3,476)	17,734	137,234	100,189
Ending balance	177,601	64,884	177,601	64,884
Unrealized Gains and Losses on Available-for-Sale Debt Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	155,403	37,162	33,038	(33,128)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(1,442)	14,593	121,114	86,519
Reclassification from Accumulated Other Comprehensive Income (Loss), Current Period, Net of Tax	0	0	(191)	(1,636)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent, Total	(1,442)	14,593	120,923	84,883
Ending balance	153,961	51,755	153,961	51,755
Unrealized Gains and Losses on Pension Plan Liability [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(3,815)	(2,055)	(3,974)	(2,177)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	0	0	0	0
Reclassification from Accumulated Other Comprehensive Income (Loss), Current Period, Net of Tax	80	62	239	184
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent, Total	80	62	239	184
Ending balance	(3,735)	(1,993)	(3,735)	(1,993)
Unrealized gains and losses on cash flow hedge
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	29,489	12,043	11,303	0
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(62)	3,137	20,526	15,180
Reclassification from Accumulated Other Comprehensive Income (Loss), Current Period, Net of Tax	(2,052)	(58)	(4,454)	(58)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent, Total	(2,114)	3,079	16,072	15,122
Ending balance	$ 27,375	$ 15,122	$ 27,375	$ 15,122