Employee Benefits - Summary of Employer Contributions (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Defined Benefit Plan Disclosure [Line Items]
Company’s benefit pension plans	$ 12	$ 18	$ 62	$ 53
U.K.
Defined Benefit Plan Disclosure [Line Items]
Company’s benefit pension plans	2	2	6	4
Other
Defined Benefit Plan Disclosure [Line Items]
Company’s benefit pension plans	2	9	10	11
U.S.
Defined Benefit Plan Disclosure [Line Items]
Company’s benefit pension plans	$ 8	$ 7	$ 46	$ 38