Condensed Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Income Statement [Abstract]
Revenue	$ 528	$ 538	$ 1,076	$ 1,097
Cost of services, exclusive of depreciation and amortization	325	345	676	701
Depreciation and amortization	27	26	53	47
Gross Profit	176	167	347	349
Operating Expenses
Selling, general and administrative	130	146	234	292
Depreciation and intangible amortization	73	73	148	149
Goodwill impairment	983	0	983	0
Total Operating expenses	1,186	219	1,365	441
Operating Income (Loss) From Continuing Operations	(1,010)	(52)	(1,018)	(92)
Other (Income) Expense
(Gain) Loss from change in fair value of financial instruments	28	(52)	20	(31)
(Gain) Loss from change in fair value of tax receivable agreement	23	(31)	32	24
Interest expense	22	33	44	64
Other (income) expense, net	(7)	0	(18)	1
Total Other (income) expense, net	66	(50)	78	58
Income (Loss) From Continuing Operations Before Taxes	(1,076)	(2)	(1,096)	(150)
Income tax expense (benefit)	(3)	2	(6)	(25)
Net Income (Loss) From Continuing Operations	(1,073)	(4)	(1,090)	(125)
Net Income (Loss) From Discontinued Operations, Net of Tax	(1)	27	(9)	32
Net Income (Loss)	(1,074)	23	(1,099)	(93)
Net income (loss) attributable to noncontrolling interests	(1)	0	(1)	(2)
Net Income (Loss) Attributable to Alight, Inc.	$ (1,073)	$ 23	$ (1,098)	$ (91)
Basic and Diluted
Continuing operations, basic (in dollars per share)	$ (2.03)	$ (0.01)	$ (2.05)	$ (0.23)
Continuing operations, diluted (in dollars per share)	(2.03)	(0.01)	(2.05)	(0.23)
Discontinued operations, basic (in dollars per share)	0.00	0.05	(0.02)	0.06
Discontinued operations, diluted (in dollars per share)	0.00	0.05	(0.02)	0.06
Net income (loss), basic (in dollars per share)	(2.03)	0.04	(2.07)	(0.17)
Net income (loss), diluted (in dollars per share)	$ (2.03)	$ 0.04	$ (2.07)	$ (0.17)
Net Income (Loss)	$ (1,074)	$ 23	$ (1,099)	$ (93)
Other comprehensive income (loss), net of tax:
Change in fair value of derivatives	(5)	(8)	(13)	(5)
Foreign currency translation adjustments	0	(2)	0	(4)
Total Other comprehensive income (loss), net of tax:	(5)	(10)	(13)	(9)
Comprehensive Income (Loss) Before Noncontrolling Interests	(1,079)	13	(1,112)	(102)
Comprehensive income (loss) attributable to noncontrolling interests	(1)	0	(1)	(6)
Comprehensive Income (Loss) Attributable to Alight, Inc.	$ (1,078)	$ 13	$ (1,111)	$ (96)