Pension and Postretirement Plans - Amounts Recognized in AOCI (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2023	Dec. 31, 2022
Pension Plans, Defined Benefit [Member]
Prior service cost recognized:
Reclassification adjustments	$ 0.0	$ 0.0
Actuarial gain (loss) recognized:
Reclassification adjustments	(0.3)	0.0
Actuarial gain (loss) arising during the period	12.0	(9.4)
Other Postretirement Benefit Plans, Defined Benefit [Member]
Prior service cost recognized:
Reclassification adjustments	(0.8)	4.7
Actuarial gain (loss) recognized:
Reclassification adjustments	(4.7)	(0.8)
Actuarial gain (loss) arising during the period	$ (0.8)	$ 37.6

Amount, before tax, of reclassification adjustment from accumulated other comprehensive income (loss) for gain (loss) of defined benefit plan.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 45
-Paragraph 15
-SubTopic 10
-Topic 220
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482790/220-10-45-15

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 11
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482790/220-10-45-11

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (i)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480506/715-20-50-1

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 17A
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482790/220-10-45-17A

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