Stock Based Compensation - Schedule of Nonvested Restricted Stock Units Activity (Details) - The 2009 Stock Incentive Plan - Restricted Stock Units (RSUs) shares in Thousands	9 Months Ended
Sep. 30, 2026 $ / shares shares
Number of Awards
Unvested RSU Awards Outstanding at beginning of period (in shares)	325
Granted (in shares)	620
Vested (in shares)	(105)
Unvested RSU Awards Outstanding at end of period (in shares)	840
Weighted Average Grant Date Fair Value per Award
Unvested RSU Awards Outstanding at beginning of period (in dollars per share) \| $ / shares	$ 23.37
Granted (in dollars per share) \| $ / shares	16.92
Vested (in dollars per share) \| $ / shares	23.99
Unvested RSU Awards Outstanding at end of period (in dollars per share) \| $ / shares	$ 18.53
Executive And Other ACM Employees
Number of Awards
Granted (in shares)	500
Board of Directors
Number of Awards
Granted (in shares)	120

The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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- Definition

The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

+ Details

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- Definition

The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(ii)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

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- Definition

Per share or unit weighted-average fair value of nonvested award under share-based payment arrangement. Excludes share and unit options.

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- Definition

The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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- Definition

The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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