Revenue Recognition - Transition Disclosures, Statement of Financial Position (Details) - USD ($) $ in Millions	Sep. 30, 2018	Jan. 01, 2018	Dec. 31, 2017		Sep. 30, 2017	Dec. 31, 2016
Assets:
Notes and accounts receivable - trade (net of allowances)	$ 7,071	$ 8,295	$ 8,928
Deferred costs (current)	2,227		1,820	[1]
Prepaid expenses and other current assets	2,388		1,860	[1],[2]
Deferred taxes	4,436		4,862
Deferred costs (noncurrent)	2,581		2,136	[1]
Investments and sundry assets	2,272		2,783	[1]
Total assets	121,990		125,356
Liabilities:
Taxes	2,502		4,219
Deferred income (current)	10,704	11,493	11,552
Deferred income (noncurrent)	3,507	3,758	3,746
Total liabilities	102,071		107,631
Equity:
Retained earnings	158,612		153,126
AOCI	(27,820)		(26,592)
Total stockholders' equity	19,918		17,725		$ 19,757	$ 18,392
Total liabilities and stockholders' equity	121,990		$ 125,356
Accounting Standards Update 2014-09, Revenue from Contracts with Customers | Adjustments to convert to prior GAAP
Assets:
Notes and accounts receivable - trade (net of allowances)	574
Deferred costs (current)	(280)
Prepaid expenses and other current assets	(510)
Deferred taxes	179	(184)
Deferred costs (noncurrent)	(402)
Total assets	(439)
Liabilities:
Deferred income (current)	51
Deferred income (noncurrent)	(5)
Total liabilities	46
Equity:
Retained earnings	(507)	$ 524
AOCI	22
Total stockholders' equity	(484)
Total liabilities and stockholders' equity	(439)
Accounting Standards Update 2014-09, Revenue from Contracts with Customers | Adjusted amounts under prior GAAP
Assets:
Notes and accounts receivable - trade (net of allowances)	7,645
Deferred costs (current)	1,947
Prepaid expenses and other current assets	1,878
Deferred taxes	4,615
Deferred costs (noncurrent)	2,179
Investments and sundry assets	2,272
Total assets	121,551
Liabilities:
Taxes	2,502
Deferred income (current)	10,754
Deferred income (noncurrent)	3,502
Total liabilities	102,117
Equity:
Retained earnings	158,106
AOCI	(27,798)
Total stockholders' equity	19,434
Total liabilities and stockholders' equity	$ 121,551

[1] Recast to conform to current period presentation.

[2] Recast to reflect adoption of the FASB guidance on restricted cash.