Employee Benefits - Summary of Employer Contributions (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Defined Benefit Plan Disclosure [Line Items]
Company’s benefit pension plans	$ 29	$ 138	$ 108	$ 222
U.S.
Defined Benefit Plan Disclosure [Line Items]
Company’s benefit pension plans	7	108	30	133
U.K.
Defined Benefit Plan Disclosure [Line Items]
Company’s benefit pension plans	19	27	65	75
Other
Defined Benefit Plan Disclosure [Line Items]
Company’s benefit pension plans	$ 3	3	$ 13	14
Qualified Plan [Member] | U.S.
Defined Benefit Plan Disclosure [Line Items]
Company’s benefit pension plans		$ 100		$ 100