Employee Benefits - Summary of Employer Contributions (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Company’s benefit pension plans	$ 50	$ 35
U.K.
Defined Benefit Plan Disclosure [Line Items]
Company’s benefit pension plans	4	2
Other
Defined Benefit Plan Disclosure [Line Items]
Company’s benefit pension plans	8	2
U.S.
Defined Benefit Plan Disclosure [Line Items]
Company’s benefit pension plans	$ 38	$ 31