Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Jul. 01, 2019	Jan. 01, 2019	Jul. 01, 2018	Jan. 01, 2018
Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive income, beginning balance				$ 4,249	$ 7,017
Other comprehensive income (loss) before reclassification, net of tax				(1,105)	(22)
Amounts reclassifed from accumulated OCI, net of tax				(1,007)	(954)
Net other comprehensive income (loss), net of tax		$ (1,152)	$ (333)	(2,112)	(976)
Amounts reclassified to retained earnings						$ 0	$ 0	$ 0	$ (658)
Accumulated other comprehensive income, ending balance		2,137	5,383	2,137	5,383
Foreign Currency Translation Adjustment [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive income, beginning balance				(3,084)	(2,054)
Other comprehensive income (loss) before reclassification, net of tax				(166)	(787)
Amounts reclassifed from accumulated OCI, net of tax				0	0
Net other comprehensive income (loss), net of tax				(166)	(787)
Amounts reclassified to retained earnings									0
Accumulated other comprehensive income, ending balance		(3,250)	(2,841)	(3,250)	(2,841)
Net Unrealized Gains (Losses) on Securities [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive income, beginning balance				(2)	660
Other comprehensive income (loss) before reclassification, net of tax				67	(22)
Amounts reclassifed from accumulated OCI, net of tax				0	0
Net other comprehensive income (loss), net of tax				67	(22)
Amounts reclassified to retained earnings	[1]								(658)
Accumulated other comprehensive income, ending balance		65	(20)	65	(20)
Net Unrealized Gains (Losses) on Derivative Instruments [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive income, beginning balance				818	1,402
Other comprehensive income (loss) before reclassification, net of tax				(1,006)	257
Amounts reclassifed from accumulated OCI, net of tax	[2]			24	35
Net other comprehensive income (loss), net of tax				(982)	292
Amounts reclassified to retained earnings									0
Accumulated other comprehensive income, ending balance		(164)	1,694	(164)	1,694
Defined Benefit Postretirement Plans [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive income, beginning balance				6,517	7,009
Other comprehensive income (loss) before reclassification, net of tax				0	530
Amounts reclassifed from accumulated OCI, net of tax	[3]			(1,031)	(989)
Net other comprehensive income (loss), net of tax				(1,031)	(459)
Amounts reclassified to retained earnings									$ 0
Accumulated other comprehensive income, ending balance		$ 5,486	$ 6,550	$ 5,486	$ 6,550

[1] With the adoption of ASU 2016-01, "Financial Instruments - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Liabilities," the unrealized (gains) losses on our equity investments are reclassified to retained earnings.

[2] (Gains) losses are included in Interest expense in the consolidated statements of income (see Note 7).

[3] The amortization of prior service credits associated with postretirement benefits are included in Other income (expense) in the consolidated statements of income (see Note 6).