Accumulated Other Comprehensive Income (Loss) - AOCI Components Pre Post & Tax Effect (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Other Comprehensive Income (Loss), Before Tax:
Net Unrealized Gains (Losses) Arising During the Period	$ (245,147)	$ (68,225)
Amortization of Unrealized Holding (Gains) Losses on HTM Securities	67	125
Net Unrealized Gains (Losses) on Investment Securities	(245,080)	(68,100)
Amortization of Net Actuarial Losses (Gains)	542	662
Amortization of Prior Service Credit	(62)	(61)
Defined Benefit Plans, Net	480	601
Other Comprehensive Income (Loss)	(244,600)	(67,499)
Other Comprehensive Income (Loss), Tax Effect:
Net Unrealized Gains (Losses) Arising During the Period	(64,974)	(18,082)
Amortization of Unrealized Holding (Gains) Losses on HTM Securities	18	32
Net Unrealized Gains (Losses) on Investment Securities	(64,956)	(18,050)
Amortization of Net Actuarial Losses (Gains)	143	177
Amortization of Prior Service Credit	(16)	(17)
Defined Benefit Plans, Net	127	160
Other Comprehensive Income (Loss)	(64,829)	(17,890)
Other Comprehensive Income (Loss), Net of Tax:
Net Unrealized Gains (Losses) Arising During the Period	(180,173)	(50,143)
Amortization of Unrealized Holding (Gains) Losses on HTM Securities	49	93
Net Unrealized Gains (Losses) on Investment Securities	(180,124)	(50,050)
Amortization of Net Actuarial Losses (Gains)	399	485
Amortization of Prior Service Credit	(46)	(44)
Defined Benefit Plans, Net	353	441
Total Other Comprehensive Loss	$ (179,771)	$ (49,609)