Pension and Other Postretirement Benefit Plans - Recurring Fair Value Measures, Activity in Level 3 (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Pension [Member]
Activity in Level 3 [Roll Forward]
Fair Value, Beginning of Year	$ 745.7	$ 759.4
Fair Value, End of Year	568.6	745.7
Pension [Member] | Level 3 [Member]
Activity in Level 3 [Roll Forward]
Fair Value, Beginning of Year	21.6
Fair Value, End of Year	22.4	21.6
Pension [Member] | Private Equity [Member] | Level 3 [Member]
Activity in Level 3 [Roll Forward]
Fair Value, Beginning of Year	0.0	7.0
Defined Benefit Plan, Plan Assets Level 3 Reconciliation, Increase (Decrease) for Actual Return (Loss) on Plan Assets Still Held		(3.5)
Defined Benefit Plan, Plan Assets Level 3 Reconciliation, Increase (Decrease) for Purchase, Sale, and Settlement		(3.5)
Fair Value, End of Year		0.0
Pension [Member] | Real Estate [Member]
Activity in Level 3 [Roll Forward]
Fair Value, Beginning of Year	21.6
Fair Value, End of Year	22.4	21.6
Pension [Member] | Real Estate [Member] | Level 3 [Member]
Activity in Level 3 [Roll Forward]
Fair Value, Beginning of Year	21.6	18.0
Defined Benefit Plan, Plan Assets Level 3 Reconciliation, Increase (Decrease) for Actual Return (Loss) on Plan Assets Still Held	1.0	3.6
Defined Benefit Plan, Plan Assets Level 3 Reconciliation, Increase (Decrease) for Purchase, Sale, and Settlement	(0.2)	0.0
Fair Value, End of Year	22.4	21.6
Postretirement Health and Life [Member]
Activity in Level 3 [Roll Forward]
Fair Value, Beginning of Year	201.8	186.0
Fair Value, End of Year	162.6	201.8
Postretirement Health and Life [Member] | Level 3 [Member]
Activity in Level 3 [Roll Forward]
Fair Value, Beginning of Year	2.0
Fair Value, End of Year	0.0	2.0
Postretirement Health and Life [Member] | Private Equity [Member]
Activity in Level 3 [Roll Forward]
Fair Value, Beginning of Year	2.0
Fair Value, End of Year		2.0
Postretirement Health and Life [Member] | Private Equity [Member] | Level 3 [Member]
Activity in Level 3 [Roll Forward]
Fair Value, Beginning of Year	2.0	1.7
Defined Benefit Plan, Plan Assets Level 3 Reconciliation, Increase (Decrease) for Actual Return (Loss) on Plan Assets Still Held	(1.5)	0.8
Defined Benefit Plan, Plan Assets Level 3 Reconciliation, Increase (Decrease) for Purchase, Sale, and Settlement	(0.5)	(0.5)
Fair Value, End of Year	$ 0.0	$ 2.0