Lease Commitments - Lease Costs (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Operating lease cost	$ 221	$ 234
Finance lease costs
Amortization of leased assets	25	26
Interest on lease liabilities	3	2
Variable lease cost	48	60
Short-term lease cost	10	5
Sublease income	(32)	(32)
Net lease cost	$ 275	$ 295

Finance Lease, Cost1 [Abstract]

No definition available.

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- Definition

Amount of interest expense on finance lease liability.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
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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
-Name Accounting Standards Codification
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-SubTopic 20
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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

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
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-Topic 842
-SubTopic 20
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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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