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Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
	Mar. 09, 2018	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Jan. 01, 2018
Accumulated Other Comprehensive Income (Loss) rollforward
Beginning of period				$ 37,695
Total other comprehensive income (loss)		$ (12)	$ 159	301	$ 158
End of period		36,622		36,622
Payments received from termination of cash flow hedge	$ 446			446
Gains recorded in accumulated other comprehensive income	331
Cash flow hedge gains expected to be reclassified in next 12 months				18
Foreign Currency
Accumulated Other Comprehensive Income (Loss) rollforward
Beginning of period		(155)	(129)		(127)
Beginning of the year, adjusted						$ (129)
Other comprehensive income (loss) before reclassifications		(8)	8	(34)	6
Total other comprehensive income (loss)		(8)	8	(34)	6
End of period		(163)	(121)	(163)	(121)
Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) rollforward
Beginning of period		321	(4)		(5)
Beginning of the year, adjusted						(18)
Other comprehensive income (loss) before reclassifications				344
Amounts reclassified from accumulated other comprehensive income (loss)		(4)		(9)	1
Total other comprehensive income (loss)		(4)		335	1
End of period		317	(4)	317	(4)
Pension and Other Postretirement Benefits
Accumulated Other Comprehensive Income (Loss) rollforward
Beginning of period		(25)	(173)		(173)
Beginning of the year, adjusted						(25)
Amounts reclassified from accumulated other comprehensive income (loss)			151		151
Total other comprehensive income (loss)			151		151
End of period		(25)	(22)	(25)	(22)
Accumulated Other Comprehensive Income (Loss).
Accumulated Other Comprehensive Income (Loss) rollforward
Beginning of period		141	(306)		(305)
Beginning of the year, adjusted						(172)
Other comprehensive income (loss) before reclassifications		(8)	8	310	6
Amounts reclassified from accumulated other comprehensive income (loss)		(4)	151	(9)	152
Total other comprehensive income (loss)		(12)	159	301	158
End of period		$ 129	$ (147)	129	$ (147)
Adjustments Early Adoption \| ASU 2018-02 \| Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) rollforward
Retained earnings adjustment						(3)
Adjustments Early Adoption \| ASU 2018-02 \| Pension and Other Postretirement Benefits
Accumulated Other Comprehensive Income (Loss) rollforward
Retained earnings adjustment						(4)
Adjustments Early Adoption \| ASU 2018-02 \| Accumulated Other Comprehensive Income (Loss).
Accumulated Other Comprehensive Income (Loss) rollforward
Retained earnings adjustment						$ (7)
Previously Reported \| Foreign Currency
Accumulated Other Comprehensive Income (Loss) rollforward
Beginning of period				(129)
Previously Reported \| Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) rollforward
Beginning of period				(15)
Previously Reported \| Pension and Other Postretirement Benefits
Accumulated Other Comprehensive Income (Loss) rollforward
Beginning of period				(21)
Previously Reported \| Accumulated Other Comprehensive Income (Loss).
Accumulated Other Comprehensive Income (Loss) rollforward
Beginning of period				$ (165)
Unsecured senior notes of $40 billion
Accumulated Other Comprehensive Income (Loss) rollforward
Aggregate Principal	$ 40,000