Benefit Plans - Pension Plans with Accumulated Benefit Obligation or Projected Benefit Obligation in Excess of Plan Assets (Detail) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Pension plans with a projected benefit obligation in excess of plan assets:
Projected benefit obligation	$ 97.5	$ 88.1
Fair value of plan assets	30.5	25.9
Pension plans with an accumulated benefit obligation in excess of plan assets:
Projected benefit obligation	83.5	78.0
Fair value of plan assets	18.8	16.5
Accumulated benefit obligation	$ 81.9	$ 77.7

Amount of plan asset for defined benefit pension plan with projected benefit obligation in excess of plan assets.

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- Definition

Amount of projected benefit obligation for defined benefit pension plan with projected benefit obligation in excess of plan assets.

+ References

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- Definition

Amount of accumulated benefit obligation for defined benefit plan with accumulated benefit obligation in excess of plan assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 17
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480482/715-20-55-17

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480506/715-20-50-3

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

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- Definition

Amount of plan asset for defined benefit plan with accumulated benefit obligation in excess of plan assets.

+ References

+ Details

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- Definition

Amount of projected benefit obligation for defined benefit pension plan with accumulated benefit obligation in excess of plan assets.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480506/715-20-50-3

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