Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Millions	Total	Total Alight, Inc. Equity	Common Stock	Treasury Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Loss	Noncontrolling Interest
Beginning balance at Dec. 31, 2023	$ 4,742	$ 4,462	$ 0	$ (52)	$ 4,946	$ (503)	$ 71	$ 280
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss)	(93)	(91)				(91)		(2)
Other comprehensive income (loss), net	(9)	(6)					(6)	(4)
Common stock issued under ESPP	6	6			6
Conversion of non-controlling interest	(71)	198			198			(269)
Share-based compensation expense	46	46			46
Shares withheld in lieu of taxes	(58)	(58)			(58)
Share repurchases	(80)	(80)		(80)
Other	(5)	(4)			(4)			(1)
Ending balance at Jun. 30, 2024	4,477	4,473	0	(132)	5,134	(594)	65	4
Beginning balance at Mar. 31, 2024	4,528	4,519	0	(52)	5,113	(617)	75	9
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss)	23	23				23
Other comprehensive income (loss), net	(10)	(10)					(10)
Common stock issued under ESPP	6	6			6
Conversion of non-controlling interest	(6)	(1)			(1)			(5)
Share-based compensation expense	18	18			18
Shares vested, net of shares withheld in lieu of taxes	(1)	(1)			(1)
Share repurchases	(80)	(80)		(80)
Other	(1)	(1)			(1)
Ending balance at Jun. 30, 2024	4,477	4,473	0	(132)	5,134	(594)	65	4
Beginning balance at Dec. 31, 2024	4,313	4,309	0	(219)	5,141	(660)	47	4
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss)	(1,099)	(1,098)				(1,098)		(1)
Other comprehensive income (loss), net	(13)	(13)					(13)
Common stock issued under ESPP	4	4			4
Share-based compensation expense	11	11			11
Shares withheld in lieu of taxes	(11)	(11)			(11)
Share repurchases	(40)	(40)		(40)
Dividends	(43)	(43)			(43)
Other	(1)	(1)			(1)
Ending balance at Jun. 30, 2025	3,121	3,118	0	(259)	5,101	(1,758)	34	3
Beginning balance at Mar. 31, 2025	4,233	4,229	0	(239)	5,114	(685)	39	4
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss)	(1,074)	(1,073)				(1,073)		(1)
Other comprehensive income (loss), net	(5)	(5)					(5)
Common stock issued under ESPP	4	4			4
Share-based compensation expense	5	5			5
Shares withheld in lieu of taxes	0	0			0
Share repurchases	(20)	(20)		(20)
Dividends	(22)	(22)			(22)
Ending balance at Jun. 30, 2025	$ 3,121	$ 3,118	$ 0	$ (259)	$ 5,101	$ (1,758)	$ 34	$ 3