Accounting Changes - Intra-Entity Transfers (Details) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended
	Jan. 31, 2017 item	Sep. 30, 2018 USD ($) $ / shares	Sep. 30, 2017 USD ($) $ / shares	Sep. 30, 2018 USD ($) item $ / shares	Sep. 30, 2017 USD ($) $ / shares	Dec. 31, 2017 USD ($)		Jan. 01, 2017 USD ($)
Accounting Changes
Investments and sundry assets		$ 2,272		$ 2,272		$ 2,783	[1]
Prepaid expenses and other current assets		2,388		2,388		1,860	[1],[2]
Deferred tax assets		4,436		4,436		4,862
Retained earnings		158,612		158,612		$ 153,126
Provision for (benefit from) income taxes		304	$ 339	138	$ 120
Income from continuing operations		2,692	2,726	6,770	6,811
Net income		$ 2,694	$ 2,726	$ 6,777	$ 6,807
Earnings per share, basic (in dollars per share) | $ / shares		$ 2.95	$ 2.93	$ 7.40	$ 7.28
Earnings per share, diluted (in dollars per share) | $ / shares		$ 2.94	$ 2.92	$ 7.37	$ 7.24
Accounting Standards Update 2016-16, Intra-Entity Transfers of Assets Other Than Inventory
Accounting Changes
Number of transactions within scope of new guidance | item				0
Accounting Standards Update 2016-16, Intra-Entity Transfers of Assets Other Than Inventory | Early adoption
Accounting Changes
Investments and sundry assets								$ (95)
Prepaid expenses and other current assets								(47)
Deferred tax assets								244
Retained earnings								$ 102
Number of transactions within scope of new guidance | item	1
Provision for (benefit from) income taxes					$ (582)
Income from continuing operations					582
Net income					$ 582
Earnings per share, basic (in dollars per share) | $ / shares					$ 0.62
Earnings per share, diluted (in dollars per share) | $ / shares					$ 0.62

[1] Recast to conform to current period presentation.

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