Employee Benefits - Benefit Obligation (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	$ 1,987
Fair value of plan assets at end of year	1,960	$ 1,987
Amounts recognized in consolidated balance sheets:
Non-current liabilities	(259)	(229)
Retirement Plans
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Net benefit obligation at beginning of year	2,076	2,329
Service cost	3	3	$ 3
Interest cost	64	71	74
Plan participants’ contributions	0	0
Actuarial loss (gain)	232	(199)
Gross benefits paid	(75)	(103)
Foreign currency effect	13	(26)
Other adjustments	(368)	1
Net benefit obligation at end of year	1,945	2,076	2,329
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	1,987	2,219
Actual return on plan assets	354	(113)
Employer contributions	46	9
Plan participants’ contributions	0	0
Gross benefits paid	(75)	(103)
Foreign currency effect	16	(25)
Other adjustments	(368)	0
Fair value of plan assets at end of year	1,960	1,987	2,219
Funded status	15	(89)
Amounts recognized in consolidated balance sheets:
Non-current assets	259	125
Current liabilities	(10)	(9)
Non-current liabilities	(234)	(205)
Total amounts recognized in consolidated balance sheets	15	(89)
Accumulated benefit obligation	1,932	2,066
Plans with accumulated benefit obligation in excess of the fair value of plan assets:
Projected benefit obligation	244	214
Accumulated benefit obligation	231	204
Fair value of plan assets	0	0
Amounts recognized in accumulated other comprehensive loss, net of tax:
Net actuarial loss (gain)	355	460
Prior service credit	2	2
Total recognized	357	462
Postretirement Plans
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Net benefit obligation at beginning of year	40	49
Service cost	0	0	0
Interest cost	1	1	2
Plan participants’ contributions	2	3
Actuarial loss (gain)	1	(4)
Gross benefits paid	(6)	(8)
Foreign currency effect	0	0
Other adjustments	0	(1)
Net benefit obligation at end of year	38	40	49
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	16	20
Actual return on plan assets	1	0
Employer contributions	0	1
Plan participants’ contributions	3	3
Gross benefits paid	(7)	(8)
Foreign currency effect	0	0
Other adjustments	0	0
Fair value of plan assets at end of year	13	16	$ 20
Funded status	(25)	(24)
Amounts recognized in consolidated balance sheets:
Non-current assets	0	0
Current liabilities	0	0
Non-current liabilities	(25)	(24)
Total amounts recognized in consolidated balance sheets	(25)	(24)
Amounts recognized in accumulated other comprehensive loss, net of tax:
Net actuarial loss (gain)	(40)	(41)
Prior service credit	(13)	(14)
Total recognized	$ (53)	$ (55)