Accumulated Other Comprehensive Income (Changes in AOCI by Component) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	$ 77,728	$ 137,207	$ 182,195	$ 40,367
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	21,850	45,471	(80,755)	143,144
Reclassification from Accumulated Other Comprehensive Income (Loss), Current Period, Net of Tax	(2,469)	(1,601)	(4,331)	(2,434)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent, Total	19,381	43,870	(85,086)	140,710
Ending balance	97,109	181,077	97,109	181,077
Unrealized Gains and Losses on Available-for-Sale Debt Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	60,569	112,543	163,174	33,038
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	21,850	42,860	(80,755)	122,556
Reclassification from Accumulated Other Comprehensive Income (Loss), Current Period, Net of Tax	(586)	0	(586)	(191)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent, Total	21,264	42,860	(81,341)	122,365
Ending balance	81,833	155,403	81,833	155,403
Unrealized Gains and Losses on Pension Plan Liability [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(5,718)	(3,894)	(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	115	79	230	159
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent, Total	115	79	230	159
Ending balance	(5,603)	(3,815)	(5,603)	(3,815)
Unrealized gains and losses on cash flow hedge
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	22,877	28,558	24,854	11,303
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	0	2,611	0	20,588
Reclassification from Accumulated Other Comprehensive Income (Loss), Current Period, Net of Tax	(1,998)	(1,680)	(3,975)	(2,402)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent, Total	(1,998)	931	(3,975)	18,186
Ending balance	$ 20,879	$ 29,489	$ 20,879	$ 29,489