Retirement Benefit Plans - Narrative (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
Actual contribution to defined benefit pension plans			$ 10
Pension settlement loss			0	$ (26)
US | Pension benefits
Defined Benefit Plan Disclosure
Defined benefit plan, benefit obligation, payment for settlement		$ 50
Liquidation of plan assets		50
Decrease in benefit obligation		63
Pension settlement loss	$ 0	(26)	0	$ (26)
US | Pension benefits | Former Employees
Defined Benefit Plan Disclosure
Defined benefit plan, benefit obligation, benefits paid		$ 13
Minimum
Defined Benefit Plan Disclosure
Defined benefit plan, expected future employer contributions, current fiscal year	15		15
Maximum
Defined Benefit Plan Disclosure
Defined benefit plan, expected future employer contributions, current fiscal year	$ 20		$ 20