Goodwill and Intangible Assets, Net - Summary of Changes in Net Carrying Amount of Goodwill (Details) $ in Millions	3 Months Ended
	Mar. 31, 2022 USD ($)
Goodwill [Line Items]
Balance as of December 31, 2021	$ 3,638
Measurement period adjustments	(10)
Foreign currency translation	(1)
Balance as of March 31, 2022	3,627
Employer Solutions
Goodwill [Line Items]
Balance as of December 31, 2021	3,564
Measurement period adjustments	(10)
Foreign currency translation	(1)
Balance as of March 31, 2022	3,553
Professional Services
Goodwill [Line Items]
Balance as of December 31, 2021	74
Balance as of March 31, 2022	$ 74