Changes in Accumulated Other Comprehensive Income - Schedule of Changes in AOCI (Details) - USD ($) $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	$ 33,907	$ 33,704	$ 33,070	$ 32,839	$ 32,565	$ 32,187	$ 33,070	$ 32,187
Beginning Balance			30,764				30,764
Other comprehensive income	30			52			33	169
Ending balance	34,352	33,907	33,704	33,388	32,839	32,565	34,352	33,388
Ending Balance	32,023						32,023
Gains (Losses) on Cash Flow Hedges
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(2)		(2)	(2)		(14)	(2)	(14)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	0			0			0	11
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0			0			0	1
Other comprehensive income	0			0			0	12
Ending balance	(2)	(2)		(2)	(2)		(2)	(2)
Gains (Losses) on Cash Flow Hedges | Accounting Standards Update 2016-01 [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Impact of adoption of Recognition and Measurement of Financial Assets and Liabilities standard(c)								0
Unrealized Gains (Losses) on Marketable Securities
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance						10		10
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax								0
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax								0
Other comprehensive income								0
Ending balance				0				0
Unrealized Gains (Losses) on Marketable Securities | Accounting Standards Update 2016-01 [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Impact of adoption of Recognition and Measurement of Financial Assets and Liabilities standard(c)								(10)
Pension and Non-Pension Postretirement Benefit Plan Items
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(2,957)		(2,960)	(2,890)		(2,998)	(2,960)	(2,998)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	6			5			(32)	22
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	21			45			62	136
Other comprehensive income	27			50			30	158
Ending balance	(2,930)	(2,957)		(2,840)	(2,890)		(2,930)	(2,840)
Pension and Non-Pension Postretirement Benefit Plan Items | Accounting Standards Update 2016-01 [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Impact of adoption of Recognition and Measurement of Financial Assets and Liabilities standard(c)								0
Foreign Currency Items
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(29)		(33)	(29)		(23)	(33)	(23)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(2)			2			2	(4)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0			0			0	0
Other comprehensive income	(2)			2			2	(4)
Ending balance	(31)	(29)		(27)	(29)		(31)	(27)
Foreign Currency Items | Accounting Standards Update 2016-01 [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Impact of adoption of Recognition and Measurement of Financial Assets and Liabilities standard(c)								0
AOCI of Investments in Unconsolidated Affiliates
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(2)		0	0		(1)	0	(1)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	0			0			(2)	1
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	2			0			2	0
Other comprehensive income	2			0			0	1
Ending balance	0	(2)		0	0		0	0
AOCI of Investments in Unconsolidated Affiliates | Accounting Standards Update 2016-01 [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Impact of adoption of Recognition and Measurement of Financial Assets and Liabilities standard(c)								0
Total
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(2,990)	(3,012)	(2,995)	(2,921)	(2,965)	(3,026)	(2,995)	(3,026)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	4			7			(32)	30
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	23			45			64	137
Other comprehensive income	27	22	(17)	52	44	71	32	167
Ending balance	$ (2,963)	$ (2,990)	$ (3,012)	$ (2,869)	$ (2,921)	$ (2,965)	$ (2,963)	(2,869)
Total | Accounting Standards Update 2016-01 [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Impact of adoption of Recognition and Measurement of Financial Assets and Liabilities standard(c)								$ (10)