Accumulated Other Comprehensive Income (Changes in AOCI by Component) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	$ 97,109	$ 181,077	$ 182,195	$ 40,367
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(22,022)	(1,504)	(102,777)	141,640
Reclassification from Accumulated Other Comprehensive Income (Loss), Current Period, Net of Tax	(2,370)	(1,972)	(6,701)	(4,406)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent, Total	(24,392)	(3,476)	(109,478)	137,234
Ending balance	72,717	177,601	72,717	177,601
Unrealized Gains and Losses on Available-for-Sale Debt Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	81,833	155,403	163,174	33,038
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(22,022)	(1,442)	(102,777)	121,114
Reclassification from Accumulated Other Comprehensive Income (Loss), Current Period, Net of Tax	(465)	0	(1,051)	(191)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent, Total	(22,487)	(1,442)	(103,828)	120,923
Ending balance	59,346	153,961	59,346	153,961
Unrealized Gains and Losses on Pension Plan Liability [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(5,603)	(3,815)	(5,833)	(3,974)
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	114	80	344	239
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent, Total	114	80	344	239
Ending balance	(5,489)	(3,735)	(5,489)	(3,735)
Unrealized gains and losses on cash flow hedge
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	20,879	29,489	24,854	11,303
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	0	(62)	0	20,526
Reclassification from Accumulated Other Comprehensive Income (Loss), Current Period, Net of Tax	(2,019)	(2,052)	(5,994)	(4,454)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent, Total	(2,019)	(2,114)	(5,994)	16,072
Ending balance	$ 18,860	$ 27,375	$ 18,860	$ 27,375