Employee Benefit Plans (Changes in Benefit Obligations and Plan Assets) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Pension Benefits
Change in benefit obligations:
Benefit obligations at beginning of year	$ 423,400	$ 443,600
Service cost	27,200	28,200	$ 27,700
Interest cost	10,700	9,500	11,000
Plan participants’ contributions	0	0
Actuarial (gain) loss	(124,600)	(19,400)
Benefits paid	(2,500)	(29,200)
Settlement payments	(57,300)	(9,300)
Benefit obligations at end of year	276,900	423,400	443,600
Change in plan assets:
Fair value of plan assets at beginning of year	294,500	295,700
Employer contributions	39,000	27,600
Plan participants’ contributions	0	0
Actual return on plan assets	(74,700)	9,700
Benefits paid	(2,500)	(29,200)
Settlement payments	(57,300)	(9,300)
Fair value of plan assets at end of year	199,000	294,500	295,700
Funded status at end of year	(77,900)	(128,900)
Accumulated benefit obligations	211,500	305,000
Other Postretirement Benefits
Change in benefit obligations:
Benefit obligations at beginning of year	17,800	17,300
Service cost	300	300	300
Interest cost	400	400	500
Plan participants’ contributions	800	800
Actuarial (gain) loss	(6,600)	900
Benefits paid	(2,000)	(1,900)
Settlement payments	0	0
Benefit obligations at end of year	10,700	17,800	17,300
Change in plan assets:
Fair value of plan assets at beginning of year	0	0
Employer contributions	1,200	1,100
Plan participants’ contributions	800	800
Actual return on plan assets	0	0
Benefits paid	(2,000)	(1,900)
Settlement payments	0	0
Fair value of plan assets at end of year	0	0	$ 0
Funded status at end of year	$ (10,700)	$ (17,800)