Schedule II Valuation and Qualifying Accounts (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance for doubtful accounts
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of period	$ 101	$ 105	$ 89
Additions, charged (credited) to income	12	10	32
Additions, charged (credited) to AOCL	0	0	0
Deductions from reserves	(6)	(13)	(8)
Translation adjustment during period	9	(1)	(8)
Balance at end of period	116	101	105
Valuation allowance — deferred tax assets
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of period	326	621	632
Additions, charged (credited) to income	(19)	(309)	31
Additions, charged (credited) to AOCL	0	2	8
Deductions from reserves	0	0	(4)
Translation adjustment during period	11	12	(46)
Balance at end of period	$ 318	$ 326	$ 621