Information Relating to the Consolidated Statement of Cash Flows (Details 2) - USD ($) $ in Millions		Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Supplemental Cash Flow Elements [Abstract]
Cash and Cash Equivalents		$ 9,686	$ 4,813	$ 6,641	$ 6,988
Restricted cash included in Prepaid expenses and other current assets		277	405	523	488
Restricted cash included in Deferred charges and other assets		778	725	791	938
Total Cash, Cash Equivalents and Restricted Cash	[1]	$ 10,741	$ 5,943	$ 7,955	$ 8,414

[1] 2017 adjusted to conform to Accounting Standards Update 2016-18. Refer to Note 4, "Information Relating to the Consolidated Statement of Cash Flows" beginning on page 8.