Business Combination, Consideration Transferred, Amount Funded with New Borrowings

No definition available.

Name:	aca_BusinessCombinationConsiderationTransferredAmountFundedwithNewBorrowings
Namespace Prefix:	aca_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Number of Divestitures

+ References

No definition available.

+ Details

Name:	aca_NumberofDivestitures
Namespace Prefix:	aca_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3602-108585

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 45
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=109226348&loc=d3e2420-110228

+ Details

Name:	us-gaap_AssetImpairmentCharges
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_BusinessAcquisitionLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 30
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=116859721&loc=d3e6613-128477

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 30
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=116859721&loc=d3e6578-128477

+ Details

Name:	us-gaap_BusinessCombinationConsiderationTransferred1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

This element represents the amount of revenue of the acquiree since the acquisition date included in the consolidated income statement for the reporting period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(1)
-URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463

+ Details

Name:	us-gaap_BusinessCombinationProFormaInformationRevenueOfAcquireeSinceAcquisitionDateActual
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=108376223&loc=d3e13816-109267

+ Details

Name:	us-gaap_GoodwillAcquiredDuringPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The number of businesses acquired by the entity during the period.

+ References

No definition available.

+ Details

Name:	us-gaap_NumberOfBusinessesAcquired
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

The cash outflow associated with the acquisition of a business, net of the cash acquired from the purchase.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3213-108585

+ Details

Name:	us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Value of stock issued pursuant to acquisitions during the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21463-112644

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.29-31)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_StockIssuedDuringPeriodValueAcquisitions
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	us-gaap_BusinessAcquisitionAxis=aca_ACGMaterialsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=aca_ConstructionProductsGroupMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=aca_LightweightaggregatesbusinessMay2017Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=aca_TrenchShoringProductsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=aca_TransportationProductsGroupMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=aca_InlandbargecomponentsbusinessMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=aca_InlandbargebusinessMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=aca_TransportationProductsGroupandConstructionProductsGroupDomain
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=aca_InlandbargecomponentsandconstructionaggregatesbusinessMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=aca_ConstructionaggregatesDomain
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=aca_EnergyEquipmentGroupMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=us-gaap_RevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=aca_CherryIndustriesInc.Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Acquisitions and Divestitures - Narrative (Details) $ in Millions		1 Months Ended				3 Months Ended				12 Months Ended
	Jan. 06, 2020 USD ($)	Dec. 31, 2018 USD ($)	Mar. 31, 2018 USD ($)	Jul. 31, 2017 USD ($)	May 31, 2017 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2019 USD ($) businesses_divested	Dec. 31, 2018 USD ($) businesses_divested	Dec. 31, 2017 USD ($) businesses_divested
Business Acquisition [Line Items]
Purchase price										$ 39.2	$ 334.1	$ 63.0
Net cash paid										32.9	333.2	47.5
Goodwill recorded										12.6	120.9	25.0
Stock issued for acquisition (value)												14.7
Impairment charge						$ 0.0	$ 23.2	$ 0.0	$ 0.0	$ 0.0	23.2	$ 0.0
Number of divestitures \| businesses_divested										0		0
Number of businesses acquired \| businesses_divested										0		0
ACG Materials
Business Acquisition [Line Items]
Revenues from acquiree included in Statement of Operations		$ 11.7
Construction Products Group \| ACG Materials
Business Acquisition [Line Items]
Purchase price											$ 309.1
Construction Products Group \| Lightweight aggregates business
Business Acquisition [Line Items]
Purchase price					$ 6.2
Construction Products Group \| Trench shoring products business
Business Acquisition [Line Items]
Purchase price				$ 42.1
Transportation Products Group \| Inland barge components business
Business Acquisition [Line Items]
Goodwill recorded										$ 12.2
Transportation Products Group \| Inland barge business
Business Acquisition [Line Items]
Purchase price			$ 25.0
Goodwill recorded			$ 9.5
Transportation Products Group and Construction Products Group \| Inland barge components and construction aggregates business
Business Acquisition [Line Items]
Purchase price										39.2
Transportation Products Group and Construction Products Group \| Construction aggregates business
Business Acquisition [Line Items]
Goodwill recorded										$ 0.4
Energy Equipment Group
Business Acquisition [Line Items]
Number of divestitures \| businesses_divested											2
Number of businesses acquired \| businesses_divested											0
Revolving credit facility \| ACG Materials
Business Acquisition [Line Items]
Borrowing to fund acquisition purchase price											$ 180.0
Subsequent event \| Construction Products Group \| Cherry Industries, Inc.
Business Acquisition [Line Items]
Purchase price	$ 298.0
Subsequent event \| Revolving credit facility \| Cherry Industries, Inc.
Business Acquisition [Line Items]
Borrowing to fund acquisition purchase price	$ 150.0