Employee Benefits - Additional Information (Details) £ in Millions, $ in Millions	3 Months Ended	9 Months Ended
	Jun. 30, 2020 GBP (£)	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)
U.K.
Defined Benefit Plan Disclosure [Line Items]
Non-cash settlement charge	£ 2	$ 0	$ 2
Expected future employer cash contribution		8
Other
Defined Benefit Plan Disclosure [Line Items]
Non-cash settlement charge		0	0
Expected future employer cash contribution		19
U.S.
Defined Benefit Plan Disclosure [Line Items]
Non-cash settlement charge		0	$ 0
Expected future employer cash contribution		$ 73