Condensed Consolidated Statements of Members' Equity (Unaudited) - Alight Holdings - USD ($) $ in Millions	Total	Common Class A	Common Class A-1 Units	Common Class B Units	Accumulated Other Comprehensive (Loss) Income
Balance at Dec. 31, 2020	$ 683	$ 699	$ 12	$ 14	$ (42)
Balance, units at Dec. 31, 2020		123,700	1,800	1,736
Comprehensive (loss) income, net of tax		$ (21)			21
Restricted share units vested, net of units withheld in lieu of taxes, units			1	50
Unit repurchases	(2)		$ (1)	$ (1)
Unit repurchases, units			(75)	(89)
Share-based compensation expense	2			$ 2
Balance at Mar. 31, 2021	683	$ 678	$ 11	$ 15	(21)
Balance, units at Mar. 31, 2021		123,700	1,726	1,697
Balance at Dec. 31, 2020	683	$ 699	$ 12	$ 14	(42)
Balance, units at Dec. 31, 2020		123,700	1,800	1,736
Comprehensive (loss) income, net of tax	6
Balance at Jun. 30, 2021	691	$ 674	$ 11	$ 17	(11)
Balance, units at Jun. 30, 2021		123,700	1,817	2,088
Balance at Mar. 31, 2021	683	$ 678	$ 11	$ 15	(21)
Balance, units at Mar. 31, 2021		123,700	1,726	1,697
Comprehensive (loss) income, net of tax	6	$ (4)			10
Restricted share units vested, net of units withheld in lieu of taxes	(1)		$ (1)
Restricted share units vested, net of units withheld in lieu of taxes, units			91	391
Share-based compensation expense	3		$ 1	$ 2
Balance at Jun. 30, 2021	$ 691	$ 674	$ 11	$ 17	$ (11)
Balance, units at Jun. 30, 2021		123,700	1,817	2,088