Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2019	Mar. 31, 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		431	1,335
Amounts reclassifed from accumulated OCI, net of tax		(335)	(311)
Net other comprehensive income (loss), net of tax		96	1,024
Amounts reclassified to retained earnings	[1]		(655)
Accumulated other comprehensive income, ending balance		4,345	7,386
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		288	106
Amounts reclassifed from accumulated OCI, net of tax		0	0
Net other comprehensive income (loss), net of tax		288	106
Amounts reclassified to retained earnings	[1]		0
Accumulated other comprehensive income, ending balance		(2,796)	(1,948)
Net Unrealized Gains (Losses) on Available-for-Sale 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		16	(12)
Amounts reclassifed from accumulated OCI, net of tax		0	0
Net other comprehensive income (loss), net of tax		16	(12)
Amounts reclassified to retained earnings	[1]		(655)
Accumulated other comprehensive income, ending balance		14	(7)
Net Unrealized Gains (Losses) on Cash Flow Hedges [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		127	674
Amounts reclassifed from accumulated OCI, net of tax	[2]	11	12
Net other comprehensive income (loss), net of tax		138	686
Amounts reclassified to retained earnings	[1]		0
Accumulated other comprehensive income, ending balance		956	2,088
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	567
Amounts reclassifed from accumulated OCI, net of tax	[3]	(346)	(323)
Net other comprehensive income (loss), net of tax		(346)	244
Amounts reclassified to retained earnings	[1]		0
Accumulated other comprehensive income, ending balance		$ 6,171	$ 7,253

[1] With the adoption of ASU 2016-01, the unrealized (gains) losses on our equity investments are reclassifed 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).