Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Schedule of Cash Flow, Supplemental Disclosures [Line Items]
Interest paid	$ 298	$ 266
Foreign and State
Schedule of Cash Flow, Supplemental Disclosures [Line Items]
Income taxes paid	838	553
Domestic
Schedule of Cash Flow, Supplemental Disclosures [Line Items]
Tax refunds	$ 2	$ 756