Savings Plans, Pension Plans and Other Postretirement Employee Benefits (Changes in Benefit Obligation, Plan Assets and Funded Status for Pension and OPEB Plans) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Amounts recognized in the consolidated balance sheets [Abstract]
Noncurrent liabilities	$ (67,856)	$ (77,396)
Pension Plans [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of year	(232,198)	(386,205)
Service cost	(5,422)	(6,805)	$ (8,182)
Interest cost	(12,551)	(10,646)	(10,533)
Actuarial gain	86	74,445
Benefits paid	16,883	17,708
Plan settlements	0	79,305
Benefit obligation at end of year	(233,202)	(232,198)	(386,205)
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	172,246	329,796
Actual return on plan assets	20,050	(62,807)
Employer contributions and benefit payments	2,462	2,278
Benefits paid	(16,883)	(17,708)
Plan settlements	0	(79,313)
Fair value of plan assets at end of year	177,875	172,246	329,796
Amounts recognized in the consolidated balance sheets [Abstract]
Current liabilities	(2,586)	(2,517)
Noncurrent liabilities	(52,741)	(57,435)
Funded status	(55,327)	(59,952)
OPEB [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of year	(22,370)	(32,258)
Service cost	(110)	(316)	(670)
Interest cost	(1,175)	(914)	(1,267)
Actuarial gain	5,717	8,334
Benefits paid	874	2,784
Plan settlements	0	0
Benefit obligation at end of year	(17,064)	(22,370)	(32,258)
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	0	0
Actual return on plan assets	0	0
Employer contributions and benefit payments	874	2,784
Benefits paid	(874)	(2,784)
Plan settlements	0	0
Fair value of plan assets at end of year	0	0	$ 0
Amounts recognized in the consolidated balance sheets [Abstract]
Current liabilities	(1,949)	(2,409)
Noncurrent liabilities	(15,115)	(19,961)
Funded status	$ (17,064)	$ (22,370)