Employee Benefits - Additional Information (Details) £ in Millions, $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2020 USD ($)	Jun. 30, 2020 GBP (£)	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)
U.K.
Defined Benefit Plan Disclosure [Line Items]
Non-cash settlement charge	$ 2	£ 2	$ 0	$ 2	$ 0
Expected future employer cash contribution	5			5
Other
Defined Benefit Plan Disclosure [Line Items]
Non-cash settlement charge	0		0	0	0
Expected future employer cash contribution	19			19
U.S.
Defined Benefit Plan Disclosure [Line Items]
Non-cash settlement charge	0		$ 0	0	$ 0
Expected future employer cash contribution	$ 99			$ 99