Schedule II Valuation and Qualifying Accounts (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Allowance for doubtful accounts
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of period	$ 116	$ 101	$ 105
Additions, charged (credited) to income	21	12	10
Additions, charged (credited) to AOCL	0	0	0
Deductions from reserves	(19)	(6)	(13)
Translation adjustment during period	(5)	9	(1)
Balance at end of period	113	116	101
Valuation allowance — deferred tax assets
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of period	318	326	621
Additions, charged (credited) to income	18	(19)	(309)
Additions, charged (credited) to AOCL	(1)	0	2
Deductions from reserves	0	0	0
Translation adjustment during period	(18)	11	12
Balance at end of period	$ 317	$ 318	$ 326