Employee Benefit Plans (Funded Status Of Plans) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at January 1	$ 1,077,653	$ 990,406
Service cost	15,351	14,279	$ 12,767
Interest cost	29,864	34,197	37,260
Actuarial (gain) loss	(30,591)	72,080
Benefits paid	(35,967)	(33,309)
Benefit obligation at December 31	1,056,310	1,077,653	990,406
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning balance	1,235,555	976,072
Actual return on plan assets	145,720	192,792
Employer contributions	32	100,000
Benefits paid	(35,967)	(33,309)
Fair value of plan assets, ending balance	1,345,340	1,235,555	$ 976,072
Funded status	289,030	157,902
BancShares Plan
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Employer contributions	$ 32	$ 80,000