Employee Benefit Plans (Narrative) (Detail) - USD ($) shares in Millions, $ in Millions	12 Months Ended
Dec. 31, 2023	Dec. 31, 2022
Deferred compensation arrangements [Abstract]
Deferred compensation plan, maximum deferral percentage	100.00%
Assets held-in-trust	$ 130.9	$ 109.7
Unfunded liabilities	$ 151.6	136.3
Executive and management supplemental benefit plans compensation period	5 years
Revision of Prior Period Adjustment
Deferred compensation arrangements [Abstract]
Additional unfunded deferred compensation	$ 7.5	$ 9.5
Savings Plan
Deferred compensation arrangements [Abstract]
Common stock, outstanding	1.4	1.6
Percentage of plan shares in total shares outstanding	1.40%	1.50%
Unfunded Supplemental Benefit Plans
Deferred compensation arrangements [Abstract]
Cash contribution to plans during the next 12 months	$ 16.2
Unfunded Supplemental Benefit Plans \| Maximum
Deferred compensation arrangements [Abstract]
Maximum benefit rate of final average compensation under non qualified plan	30.00%
Unfunded Supplemental Benefit Plans \| Minimum
Deferred compensation arrangements [Abstract]
Maximum benefit rate of final average compensation under non qualified plan	15.00%
Defined Benefit Pension And Supplemental Benefit Plans
Deferred compensation arrangements [Abstract]
Net actuarial loss expected to be amortized from accumulated comprehensive income/loss into net periodic loss in next fiscal year	$ 2.3

Maximum salary deferral rate for employees under the deferred compensation plan.

No definition available.

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- Definition

The amount of time over which the average compensation is calculated for purposes of the defined benefit plan.

+ References

No definition available.

+ Details

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- Definition

Defined contribution plan, number of shares of equity securities issued by employer and related parties included in plan assets.

+ References

No definition available.

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- Definition

Defined contribution plan, number of shares of equity securities issued by employer and related parties included in plan assets as a percentage of total employer shares outstanding.

+ References

No definition available.

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- Definition

Maximum benefit rate of final average compensation under the nonqualified plan.

+ References

No definition available.

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- Definition

The carrying amount of the liability as of the balance sheet date to an individual under a deferred compensation arrangement. This amount may be the result of periodic accruals made over the period of active employment, or reflect termination benefits resulting contractual terms or a death benefit.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 710
-SubTopic 10
-Name Accounting Standards Codification
-Section 30
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483043/710-10-30-1

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- References

No definition available.

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- Definition

Aggregate carrying value as of the balance sheet date of the liabilities for all deferred compensation arrangements. Represents currently earned compensation under compensation arrangements that is not actually paid until a later date.

+ References

No definition available.

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- Definition

Carrying amount as of the balance sheet date of assets held under deferred compensation agreements.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(17))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1

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- Definition

Amount included in accumulated other comprehensive income (loss) for gain (loss) of defined benefit plan expected to be recognized in net periodic benefit (cost) credit for fiscal year following most recent annual statement of financial position.

+ References

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

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- Definition

Amount of contribution expected to be received by defined benefit plan from employer in next fiscal year following current fiscal year.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 18
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480482/715-20-55-18

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (g)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480506/715-20-50-1

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