Benefit Plans - Pension Obligation and Funded Status (Details) - Pension Plan - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
US
Benefit obligation
Balance at the beginning of the period	$ 387	$ 357
Service cost	5	5	$ 6
Interest cost	11	14	13
Benefits paid	(23)	(28)
Actuarial loss (gain)	29	39
Balance at the end of the period	409	387	357
Fair value of plan assets
Balance at the beginning of the period	408	353
Actual return on plan assets	53	82
Employer contributions	1	1
Benefits paid	(23)	(28)
Balance at the end of the period	439	408	353
Funded status	30	21
Non-US
Benefit obligation
Balance at the beginning of the period	254	223
Service cost	4	3	3
Interest cost	10	10	10
Benefits paid	(12)	(11)
Actuarial loss (gain)	14	24
Curtailment / settlement / amendments		(2)
Foreign currency translation	5	7
Balance at the end of the period	275	254	223
Fair value of plan assets
Balance at the beginning of the period	231	207
Actual return on plan assets	22	24
Employer contributions	4	7
Benefits paid	(12)	(11)
Plan settlements		(3)
Foreign currency translation	4	7
Balance at the end of the period	249	231	$ 207
Funded status	$ (26)	$ (23)

The amount of increase or decrease due to a) an event that significantly reduces the expected years of future service of present employees or eliminates for a significant number of employees the accrual of defined benefits for some or all of their future services, b) an irrevocable action that relieves the employer (or the plan) of primary responsibility for a benefit obligation and eliminates significant risks related to the obligation and the assets used to effect the settlement, c) change in the terms of an existing plan or the initiation of a new plan. A plan amendment may increase or decrease benefits, including those attributed to years of service already rendered.

No definition available.