Condensed Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Income Statement [Abstract]
Revenue	$ 555	$ 557	$ 1,652	$ 1,704
Cost of services, exclusive of depreciation and amortization	358	372	1,059	1,110
Depreciation and amortization	23	19	70	54
Gross Profit	174	166	523	540
Operating Expenses
Selling, general and administrative	142	136	434	436
Depreciation and intangible amortization	74	75	223	225
Total Operating expenses	216	211	657	661
Operating Income (Loss) From Continuing Operations	(42)	(45)	(134)	(121)
Other (Income) Expense
(Gain) Loss from change in fair value of financial instruments	(23)	(36)	(54)	(11)
(Gain) Loss from change in fair value of tax receivable agreement	27	11	51	30
Interest expense	19	34	83	100
Other (income) expense, net	(12)	0	(11)	1
Total Other (income) expense, net	11	9	69	120
Income (Loss) From Continuing Operations Before Taxes	(53)	(54)	(203)	(241)
Income tax expense (benefit)	(9)	(14)	(34)	(45)
Net Income (Loss) From Continuing Operations	(44)	(40)	(169)	(196)
Net Income (Loss) From Discontinued Operations (including gain on disposal of $4.0m), Net of Tax	(30)	(6)	2	4
Net Income (Loss)	(74)	(46)	(167)	(192)
Net income (loss) attributable to noncontrolling interests	0	2	(2)	(9)
Net Income (Loss) Attributable to Alight, Inc.	$ (74)	$ (48)	$ (165)	$ (183)
Basic and Diluted
Continuing operations, basic (in dollars per share)	$ (0.08)	$ (0.09)	$ (0.31)	$ (0.39)
Continuing operations, diluted (in dollars per share)	(0.08)	(0.09)	(0.31)	(0.39)
Discontinued operations, basic (in dollars per share)	(0.06)	(0.01)	0	0.01
Discontinued operations, diluted (in dollars per share)	(0.06)	(0.01)	0	0.01
Net income (loss), basic (in dollars per share)	(0.14)	(0.10)	(0.31)	(0.38)
Net income (loss), diluted (in dollars per share)	$ (0.14)	$ (0.10)	$ (0.31)	$ (0.38)
Net Income (Loss)	$ (74)	$ (46)	$ (167)	$ (192)
Other comprehensive income (loss), net of tax:
Change in fair value of derivatives	(30)	(2)	(35)	(8)
Foreign currency translation adjustments	13	(3)	8	3
Total Other comprehensive income (loss), net of tax:	(17)	(5)	(27)	(5)
Comprehensive Income (Loss) Before Noncontrolling Interests	(91)	(51)	(194)	(197)
Comprehensive income (loss) attributable to noncontrolling interests	0	1	(6)	(15)
Comprehensive Income (Loss) Attributable to Alight, Inc.	$ (91)	$ (52)	$ (188)	$ (182)