Employee Benefits - Summary of Employer Contributions (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Defined Benefit Plan Disclosure [Line Items]
Company’s benefit pension plans	$ 18	$ 32	$ 53	$ 79
U.K.
Defined Benefit Plan Disclosure [Line Items]
Company’s benefit pension plans	2	23	4	46
Other
Defined Benefit Plan Disclosure [Line Items]
Company’s benefit pension plans	9	3	11	10
U.S.
Defined Benefit Plan Disclosure [Line Items]
Company’s benefit pension plans	$ 7	$ 6	$ 38	$ 23