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Basis of Presentation - Impact of Adopting Standards (Details) - USD ($) $ in Millions	Sep. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
Assets - Increase (Decrease)
Accounts receivable	$ 7,374		$ 6,873
Liabilities - Increase (Decrease)
Income taxes payable	759		708
Debt	3,656		3,057
Deferred Income Taxes	2,065		2,219
Equity - Increase (Decrease)
Retained earnings	42,189		41,350
Accumulated other comprehensive loss	(5,151)		$ (4,910)
Adjustments for New Accounting Pronouncement
Assets - Increase (Decrease)
Accounts receivable		$ 5
Liabilities - Increase (Decrease)
Income taxes payable		(3)
Debt		14
Deferred Income Taxes		(54)
Equity - Increase (Decrease)
Retained earnings		322
Accumulated other comprehensive loss		(274)
ASU 2016-01 (Financial Instruments)
Equity - Increase (Decrease)
Retained earnings		8
Accumulated other comprehensive loss		(8)
ASU 2016-16 (Intra-Entity Transfers of Assets Other than Inventory)
Liabilities - Increase (Decrease)
Deferred Income Taxes		(54)
Equity - Increase (Decrease)
Retained earnings		54
ASU 2017-12 (Derivatives and Hedging)
Liabilities - Increase (Decrease)
Income taxes payable		(3)
Debt		14
Equity - Increase (Decrease)
Retained earnings		(11)
ASU 2018-02 (Reclassification of Certain Tax Effects)
Equity - Increase (Decrease)
Retained earnings		266
Accumulated other comprehensive loss		(266)
Effects of Adopting ASC 606 \| ASU 2014-09 (Revenue)
Assets - Increase (Decrease)
Accounts receivable	(45)	5
Liabilities - Increase (Decrease)
Income taxes payable	(5)
Equity - Increase (Decrease)
Retained earnings	$ (15)	$ 5