Leases - Summary of Lease Cost (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2019
Lease Cost [Abstract]
Operating lease cost	$ 117	$ 234
Finance lease cost
Amortization of leased assets	1	1
Interest on lease liabilities	1	1
Variable lease cost	80	171
Short-term lease cost	2	5
Sublease income	(7)	(14)
Total lease cost	$ 194	$ 398

No definition available.

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- Definition

Amount of interest expense on finance lease liability.

+ References

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-Publisher FASB
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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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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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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- Definition

Amount of short-term lease cost, excluding expense for lease with term of one month or less.

+ References

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- Definition

Amount of sublease income excluding finance and operating lease expense.

+ References

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- Definition

Amount of variable lease cost, excluded from lease liability, recognized when obligation for payment is incurred for finance and operating leases.

+ References

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