Employee Benefits - Summary of Employer Contributions (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Company’s benefit pension plans	$ 35	$ 47
U.S.
Defined Benefit Plan Disclosure [Line Items]
Company’s benefit pension plans	31	17
U.K.
Defined Benefit Plan Disclosure [Line Items]
Company’s benefit pension plans	2	23
Other
Defined Benefit Plan Disclosure [Line Items]
Company’s benefit pension plans	$ 2	$ 7