Condensed Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Income Statement [Abstract]
Revenue	$ 533	$ 555	$ 1,609	$ 1,652
Cost of services, exclusive of depreciation and amortization	327	358	1,003	1,059
Depreciation and amortization	28	23	81	70
Gross Profit	178	174	525	523
Operating Expenses
Selling, general and administrative	87	142	321	434
Depreciation and intangible amortization	75	74	223	223
Goodwill impairment	1,338	0	2,321	0
Total Operating expenses	1,500	216	2,865	657
Operating Income (Loss) From Continuing Operations	(1,322)	(42)	(2,340)	(134)
Other (Income) Expense
(Gain) Loss from change in fair value of financial instruments	(19)	(23)	1	(54)
(Gain) Loss from change in fair value of tax receivable agreement	(66)	27	(34)	51
Interest expense	24	19	68	83
Other (income) expense, net	(8)	(12)	(26)	(11)
Total Other (income) expense, net	(69)	11	9	69
Income (Loss) From Continuing Operations Before Taxes	(1,253)	(53)	(2,349)	(203)
Income tax expense (benefit)	(198)	(9)	(204)	(34)
Net Income (Loss) From Continuing Operations	(1,055)	(44)	(2,145)	(169)
Net Income (Loss) From Discontinued Operations, Net of Tax	(13)	(30)	(22)	2
Net Income (Loss)	(1,068)	(74)	(2,167)	(167)
Net income (loss) attributable to noncontrolling interests	(1)	0	(2)	(2)
Net Income (Loss) Attributable to Alight, Inc.	$ (1,067)	$ (74)	$ (2,165)	$ (165)
Basic and Diluted
Continuing operations, basic (in dollars per share)	$ (2.00)	$ (0.08)	$ (4.05)	$ (0.31)
Continuing operations, diluted (in dollars per share)	(2.00)	(0.08)	(4.05)	(0.31)
Discontinued operations, basic (in dollars per share)	(0.02)	(0.06)	(0.04)	0.00
Discontinued operations, diluted (in dollars per share)	(0.02)	(0.06)	(0.04)	0.00
Net income (loss), basic (in dollars per share)	(2.02)	(0.14)	(4.09)	(0.31)
Net income (loss), diluted (in dollars per share)	$ (2.02)	$ (0.14)	$ (4.09)	$ (0.31)
Net Income (Loss)	$ (1,068)	$ (74)	$ (2,167)	$ (167)
Other comprehensive income (loss), net of tax:
Change in fair value of derivatives	(4)	(30)	(17)	(35)
Foreign currency translation adjustments	0	13	0	8
Total Other comprehensive income (loss), net of tax:	(4)	(17)	(17)	(27)
Comprehensive Income (Loss) Before Noncontrolling Interests	(1,072)	(91)	(2,184)	(194)
Comprehensive income (loss) attributable to noncontrolling interests	(1)	0	(2)	(6)
Comprehensive Income (Loss) Attributable to Alight, Inc.	$ (1,071)	$ (91)	$ (2,182)	$ (188)