Retirement Benefits - Textuals (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2022
Defined Benefit Plan and Other Postretirement Benefit Plans Table Text Block [Line Items]
Five-year smoothing of asset gains (losses)	5 years
Subsidiaries [Member]
Defined Benefit Plan and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Contribution Plan, Interest Credit	4.00%
Forecast | Qualified Plan | Subsidiaries [Member] | Pension Plan [Member]
Defined Benefit Plan and Other Postretirement Benefit Plans Table Text Block [Line Items]
Estimated Future Employer Contributions in Current Fiscal Year		$ 18.0
Forecast | Nonqualified Plan | Subsidiaries [Member] | Pension Plan [Member]
Defined Benefit Plan and Other Postretirement Benefit Plans Table Text Block [Line Items]
Estimated Future Employer Contributions in Current Fiscal Year		2.8
Forecast | Other Pension Plan [Member] | Subsidiaries [Member] | Pension Plan [Member]
Defined Benefit Plan and Other Postretirement Benefit Plans Table Text Block [Line Items]
Estimated Future Employer Contributions in Current Fiscal Year		$ 0.3