Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2022	May 05, 2022
Document Information [Line Items]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2022
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q1
Entity Registrant Name	Alight, Inc. / Delaware
Entity Central Index Key	0001809104
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Shell Company	false
Entity Small Business	false
Entity Emerging Growth Company	false
Title of 12(b) Security	Class A Common Stock, par value $0.0001 per share
Trading Symbol	ALIT
Security Exchange Name	NYSE
Entity File Number	001-39299
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	86-1849232
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
Document Quarterly Report	true
Document Transition Report	false
Class A Common Stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		465,225,352
Class B-1 Common Stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		4,990,453
Class B-2 Common Stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		4,990,453
Class V Common Stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		76,220,431
Class Z-A Common Stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		5,046,819
Class Z-B-1 Common Stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		274,379
Class Z-B-2 Common Stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		274,379