Current Receivables (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total current receivables, gross	$ 6,138	$ 6,345
Less: Allowance for doubtful accounts	(329)	(330)
Total current receivables, net	5,809	6,015
Customer receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total current receivables, gross	4,789	4,700
Related parties
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total current receivables, gross	675	801
Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total current receivables, gross	$ 674	$ 844