Cover Page and DEI - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Jan. 15, 2020	Jun. 30, 2019
Document Information [Line Items]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2019
Document Transition Report	false
Entity File Number	1-38494
Entity Registrant Name	Arcosa, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	82-5339416
Entity Address, Address Line One	500 N. Akard Street, Suite 400
Entity Address, City or Town	Dallas,
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	75201
City Area Code	972
Local Phone Number	942-6500
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 1,820.8
Entity Common Stock, Shares Outstanding		48,279,180
Title of 12(b) Security	Common Stock ($0.01 par value)
Trading Symbol	ACA
Security Exchange Name	NYSE
Documents Incorporated by Reference	The information required by Part III of this report, to the extent not set forth herein, is incorporated by reference from the registrant's definitive 2020 Proxy Statement.
Entity Central Index Key	0001739445
Amendment Flag	false
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Current Fiscal Year End Date	--12-31