Retirement Benefits - Amounts Recognized (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Other Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	$ 9,015	$ 11,654	$ 12,114
Accumulated benefit obligation	8,929	11,549
Fair value of plan assets	5,190	6,341	5,918
Defined Benefit Plan, Amounts Recognized in Statement of Financial Position Consist of: [Abstract]
Noncurrent assets	0	0
Current liabilities	(252)	(280)
Noncurrent liabilities	(3,573)	(5,033)
Net assets (liabilities)	(3,825)	(5,313)
Parent Company [Member] | Other Pension Plan [Member]
Defined Benefit Plan, Amounts Recognized in Accumulated Other Comprehensive Income Consist of: [Abstract]
Accumulated Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), after Tax	(1,964)	(525)
Accumulated Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), after Tax	259	242
Accumulated Other Comprehensive (Income) Loss, Defined Benefit Plan, after Tax, Total	(1,705)	(283)
Subsidiaries [Member] | Other Pension Plan [Member]
Defined Benefit Plan, Amounts Recognized in Accumulated Other Comprehensive Income Consist of: [Abstract]
Accumulated Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), after Tax	(2,056)	(622)
Accumulated Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), after Tax	258	242
Accumulated Other Comprehensive (Income) Loss, Defined Benefit Plan, after Tax, Total	(1,798)	(380)
Nonqualified Plan | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	32,046	43,155	46,742
Accumulated benefit obligation	29,763	40,773
Fair value of plan assets	0	0	0
Defined Benefit Plan, Amounts Recognized in Statement of Financial Position Consist of: [Abstract]
Noncurrent assets	0	0
Current liabilities	(3,532)	(2,822)
Noncurrent liabilities	(28,514)	(40,333)
Net assets (liabilities)	(32,046)	(43,155)
Nonqualified Plan | Parent Company [Member] | Pension Plan [Member]
Defined Benefit Plan, Amounts Recognized in Accumulated Other Comprehensive Income Consist of: [Abstract]
Accumulated Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), after Tax	1,563	9,571
Accumulated Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), after Tax	289	578
Accumulated Other Comprehensive (Income) Loss, Defined Benefit Plan, after Tax, Total	1,852	10,149
Nonqualified Plan | Subsidiaries [Member] | Pension Plan [Member]
Defined Benefit Plan, Amounts Recognized in Accumulated Other Comprehensive Income Consist of: [Abstract]
Accumulated Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), after Tax	1,864	10,103
Accumulated Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), after Tax	289	578
Accumulated Other Comprehensive (Income) Loss, Defined Benefit Plan, after Tax, Total	2,153	10,681
Qualified Plan | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	589,278	834,960	849,383
Accumulated benefit obligation	582,538	823,418
Fair value of plan assets	658,533	898,550	$ 834,655
Defined Benefit Plan, Amounts Recognized in Statement of Financial Position Consist of: [Abstract]
Noncurrent assets	69,255	63,590
Current liabilities	0	0
Noncurrent liabilities	0	0
Net assets (liabilities)	69,255	63,590
Qualified Plan | Parent Company [Member] | Pension Plan [Member]
Defined Benefit Plan, Amounts Recognized in Accumulated Other Comprehensive Income Consist of: [Abstract]
Accumulated Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), after Tax	31,213	24,859
Accumulated Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), after Tax	0	0
Accumulated Other Comprehensive (Income) Loss, Defined Benefit Plan, after Tax, Total	31,213	24,859
Qualified Plan | Subsidiaries [Member] | Pension Plan [Member]
Defined Benefit Plan, Amounts Recognized in Accumulated Other Comprehensive Income Consist of: [Abstract]
Accumulated Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), after Tax	124,767	127,111
Accumulated Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), after Tax	0	0
Accumulated Other Comprehensive (Income) Loss, Defined Benefit Plan, after Tax, Total	$ 124,767	$ 127,111