Leases - Components of Lease Cost (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Leases [Abstract]
Operating lease cost	$ 259	$ 312	$ 531	$ 638
Variable and short-term lease cost	661	669	1,267	1,280
Amortization of finance lease assets	18	17	36	40
Interest on finance lease liabilities	32	4	59	9
Sublease income	(9)	(11)	(17)	(21)
Total lease cost	$ 961	$ 991	$ 1,876	$ 1,946

Variable And Short-Term Lease, Cost

No definition available.

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- Definition

Amount of interest expense on finance lease liability.

+ References

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- Definition

Amount of amortization expense attributable to right-of-use asset from finance lease.

+ References

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- Definition

Amount of lease cost recognized by lessee for lease contract.

+ References

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- References

No definition available.

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- Definition

Amount of single lease cost, calculated by allocation of remaining cost of lease over remaining lease term. Includes, but is not limited to, single lease cost, after impairment of right-of-use asset, calculated by amortization of remaining right-of-use asset and accretion of lease liability.

+ References

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-Publisher FASB
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- Definition

Amount of sublease income excluding finance and operating lease expense.

+ References

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