Schedule II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Allowance for doubtful accounts [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of period	$ 50	$ 60	$ 62
Balance acquired through acquisitions	0	0	0
Charged to cost and expenses	13	9	14
Charged to other accounts	15	0	0
Deductions	15	19	16
Balance at end of period	63	50	60
Valuation allowance on deferred tax assets [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of period	575	634	240
Balance acquired through acquisitions	0	1	0
Charged to cost and expenses	398	36	450
Charged to other accounts	0	0	0
Deductions	54	96	56
Balance at end of period	919	575	634
Reserve for inventory obsolescence [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of period	30	35	32
Balance acquired through acquisitions	0	0	0
Charged to cost and expenses	10	8	15
Charged to other accounts	0	0	0
Deductions	17	13	12
Balance at end of period	$ 23	$ 30	$ 35