Fair Value Measurements (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Fair Value Measurements:
Debt, carrying value	$ 73,306	$ 72,827
Senior Notes and Debentures [Member]
Fair Value Measurements:
Debt, carrying value	62,217	62,868
Credit Facilities [Member]
Fair Value Measurements:
Debt, carrying value	11,089	9,959
Level 1 [Member] | Senior Notes and Debentures [Member]
Fair Value Measurements:
Debt, fair value	66,122	61,087
Level 2 [Member] | Credit Facilities [Member]
Fair Value Measurements:
Debt, fair value	11,123	9,608
Cross Currency Derivatives [Member] | Level 2 [Member]
Fair Value Measurements:
Derivative Liability	$ 323	$ 237