Shareholders' Equity (Accumulated other comprehensive income) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Balance	[1]	$ (17,133)	$ (16,153)	$ (15,083)
OCI before reclassifications	[1]	4,248	(1,817)	(1,471)
Amounts reclassified from AOCI	[1]	1,226	837	401
Net current period OCI	[1]	5,474	(980)	(1,070)
Balance	[1]	(11,659)	(17,133)	(16,153)
Defined benefit pension plans & other postretirement benefits:
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, after Tax		1,155	917	464
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, Tax		(8)	(52)	(133)
Currency Translation Adjustments [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Balance		(30)	(128)	(101)
OCI before reclassifications		(75)	98	(27)
Amounts reclassified from AOCI
Net current period OCI		(75)	98	(27)
Balance		(105)	(30)	(128)
Unrealized Gains and Losses on Certain Investments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Balance		1	1
OCI before reclassifications				1
Amounts reclassified from AOCI
Net current period OCI				1
Balance		1	1	1
Unrealized Gains and Losses on Derivative Instruments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Balance		(43)	(84)	(62)
OCI before reclassifications		55	14	(48)
Amounts reclassified from AOCI		(6)	27	26
Net current period OCI		49	41	(22)
Balance		6	(43)	(84)
Defined Benefit Pension Plans and Other Postretirement Benefits
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Balance		(17,061)	(15,942)	(14,920)
OCI before reclassifications		4,268	(1,929)	(1,397)
Amounts reclassified from AOCI		1,232	810	375	[2]
Net current period OCI		5,500	(1,119)	(1,022)
Balance		$ (11,561)	$ (17,061)	$ (15,942)

[1] Net of tax.

[2] Primarily relates to remeasurement of assets and benefit obligations related to the Company's pension and other postretirement benefit plans resulting in an actuarial gain/(loss) of $4,262, ($1,956) and ($1,413) (net of tax of ($32), $111 and $405) for the years ended December 31, 2021, 2020 and 2019. See Note 16.