Supplemental Cash Flow Information (Details) - USD ($) $ in Millions			3 Months Ended
		Jan. 01, 2019	Mar. 31, 2019	Mar. 31, 2018
Decrease (increase) in current assets:
Receivables, net			$ (895)	$ 145
Inventories			28	(126)
Prepaid expenses and other			16	(79)
Increase (decrease) in current liabilities:
Accounts payable			1,400	(322)
Accrued expenses			(167)	(131)
Taxes other than income taxes payable			(263)	(111)
Income taxes payable			11	(402)
Changes in current assets and current liabilities			130	(1,026)
Cash Flows Related to Interest and Income Taxes
Interest paid in excess of amount capitalized, including interest on finance leases			96	127
Income taxes paid, net			59	$ 552
Cash paid for amounts included in the measurement of lease liabilities:
Operating leases - operating cash flows			107
Operating leases - ROU assets obtained in exchange for new lease liabilities	[1]		1,430
Operating leases - changes in lease balances resulting from lease modifications			(26)
Cash paid for amounts included in the measurement of lease liabilities:
Finance leases - operating cash flows			11
Finance leases - financing cash flows			6
Finance leases - ROU assets obtained in exchange for new lease liabilities			$ 2
Topic 842 [Member]
Cash paid for amounts included in the measurement of lease liabilities:
Operating leases - ROU assets obtained in exchange for new lease liabilities		$ 1,300

[1] Includes noncash activity of $1.3 billion for ROU assets for operating leases recorded on January 1, 2019 upon adoption of Topic 842.