Changes in Accumulated Other Comprehensive Income - Schedule of Changes in AOCI (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	$ 33,047	$ 32,169	$ 27,629
Other comprehensive income (loss)	(198)	42	171
Ending Balance	34,573	33,047	32,169
Gains and (Losses) on Cash Flow Hedges
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	(2)	(14)	(17)
OCI before reclassifications	0	11	(1)
Amounts reclassified from AOCI	0	1	4
Other comprehensive income (loss)	0	12	3
Tax Cuts and Jobs Act, Reclassification from AOCI to Retained Earnings			0
Ending Balance	(2)	(2)	(14)
Gains and (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		0
Unrealized Gains and (Losses) on Marketable Securities
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	0	10	4
OCI before reclassifications	0	0	6
Amounts reclassified from AOCI	0	0	0
Other comprehensive income (loss)	0	0	6
Tax Cuts and Jobs Act, Reclassification from AOCI to Retained Earnings			0
Ending Balance	0	0	10
Unrealized Gains and (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		(10)
Pension and Non-Pension Postretirement Benefit Plan Items (a)
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	(2,960)	(2,998)	(2,610)
OCI before reclassifications	(289)	(143)	11
Amounts reclassified from AOCI	84	181	140
Other comprehensive income (loss)	(205)	38	151
Tax Cuts and Jobs Act, Reclassification from AOCI to Retained Earnings			(539)
Ending Balance	(3,165)	(2,960)	(2,998)
Pension and Non-Pension Postretirement Benefit Plan Items (a) | 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		0
Foreign Currency Items
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	(33)	(23)	(30)
OCI before reclassifications	6	(10)	7
Amounts reclassified from AOCI	0	0	0
Other comprehensive income (loss)	6	(10)	7
Tax Cuts and Jobs Act, Reclassification from AOCI to Retained Earnings			0
Ending Balance	(27)	(33)	(23)
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		0
AOCI of Investments Unconsolidated Affiliates (b)
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	0	(1)	(7)
OCI before reclassifications	(2)	1	6
Amounts reclassified from AOCI	2	0	0
Other comprehensive income (loss)	0	1	6
Tax Cuts and Jobs Act, Reclassification from AOCI to Retained Earnings			0
Ending Balance	0	0	(1)
AOCI of Investments Unconsolidated Affiliates (b) | 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		0
Total
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	(2,995)	(3,026)	(2,660)
OCI before reclassifications	(285)	(141)	29
Amounts reclassified from AOCI	86	182	144
Other comprehensive income (loss)	(199)	41	173
Ending Balance	$ (3,194)	(2,995)	$ (3,026)
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		$ (10)