New Accounting Standards - Effect of change related to ASU 2017-07 (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cost of sales	$ 30,288	$ 30,668	$ 96,345	$ 93,707
Selling, administrative, and other expenses	2,919	2,657	8,439	8,131
Accounting Standards Update 2017-07 [Member] | Scenario, Previously Reported [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cost of sales		30,446		93,075
Selling, administrative, and other expenses		2,535		7,758
Accounting Standards Update 2017-07 [Member] | Scenario, Adjustment [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cost of sales		222		632
Selling, administrative, and other expenses		122		373
Operating Segments [Member] | Non-Financial Services
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other income/(loss), net	$ 709	672	$ 2,079	2,126
Operating Segments [Member] | Non-Financial Services | Accounting Standards Update 2017-07 [Member] | Scenario, Previously Reported [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other income/(loss), net		328		1,121
Operating Segments [Member] | Non-Financial Services | Accounting Standards Update 2017-07 [Member] | Scenario, Adjustment [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other income/(loss), net		$ 344		$ 1,005