Cover Page - USD ($)	12 Months Ended
	Dec. 31, 2023	Apr. 24, 2024	Jun. 30, 2023
Document Information [Line Items]
Document Type	10-K/A
Document Annual Report	true
Document Transition Report	false
Entity Interactive Data Current	Yes
Amendment Flag	true
Amendment Description	Explanatory Note This Amendment No. 1 on Form 10-K/A (this “Amendment”) amends our Annual Report on Form 10-K for the year ended December 31, 2023, originally filed with the Securities and Exchange Commission (the “SEC”) on February 29, 2024 (the “Original Filing”). We are filing this Amendment pursuant to General Instruction G(3) of Form 10-K to include the information required by Part III of Form 10-K that we did not include in the Original Filing, as we do not intend to file a definitive proxy statement for an annual meeting of stockholders within 120 days of the end of our fiscal year ended December 31, 2023. This Amendment also deletes the reference on the cover of the Original Filing to the incorporation by reference of certain information from our proxy statement into Part III of the Original Filing. In addition, in connection with the filing of this Amendment and pursuant to Rule 12b-15 under the Securities Exchange Act of 1934, as amended, or the Exchange Act, we are including with this Amendment new certifications of our principal executive officer and principal financial officer pursuant to Section 302 of the Sarbanes-Oxley Act of 2002. Item 15 of Part IV has also been amended to reflect the filing of these new certifications. Except as described above, no other changes have been made to the Original Filing. The Original Filing continues to speak as of the date of the Original Filing, and we have not updated the disclosures contained therein to reflect any events which occurred at a date subsequent to the filing of the Original Filing. Unless otherwise noted or the context indicates otherwise, the terms “Alight,” the “Company,” “we,” “us,” and “our” refer to Alight, Inc., a Delaware corporation, together with its subsidiaries.
Document Period End Date	Dec. 31, 2023
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	FY
Entity Registrant Name	Alight, Inc. / Delaware
Entity Central Index Key	0001809104
Entity File Number	001-39299
Entity Tax Identification Number	86-1849232
Entity Incorporation, State or Country Code	DE
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Shell Company	false
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Public Float			$ 3,152,296,204
Entity Address, Address Line One	4 Overlook Point
Entity Address, City or Town	Lincolnshire
Entity Address, State or Province	IL
Entity Address, Postal Zip Code	60069
City Area Code	224
Local Phone Number	737-7000
Title of 12(b) Security	Class A Common Stock, par value $0.0001 per share
Trading Symbol	ALIT
Security Exchange Name	NYSE
Document Financial Statement Error Correction [Flag]	false
ICFR Auditor Attestation Flag	true
Auditor Name	Ernst & Young LLP
Auditor Firm ID	42
Auditor Location	Chicago, Illinois
Class A Common Stock [Member]
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		550,346,093
Class B-1 Common Stock [Member]
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		4,914,939
Class B-2 Common Stock [Member]
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		4,914,939
Class V Common Stock [Member]
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		734,248
Class Z-A Common Stock [Member]
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		5,046,819
Class Z-B-1 Common Stock [Member]
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		274,379
Class Z-B-2 Common Stock [Member]
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		274,379