Leases - Components of Lease Expense (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Operating lease expense
Operating lease cost	$ 124	$ 151	$ 254	$ 307
Short-term lease cost	12	11	23	26
Variable lease cost	15	15	33	23
Sublease income	(17)	(10)	(26)	(22)
Total operating costs	134	167	284	334
Finance lease expense
Amortization of right-of-use assets	99	99	186	215
Interest on lease liabilities	7	11	16	25
Total finance lease cost	$ 106	$ 110	$ 202	$ 240

Finance Lease, Cost

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Finance Lease, Cost1 [Abstract]

+ References

No definition available.

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Operating Lease, Cost

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No definition available.

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- Definition

Amount of interest expense on finance lease liability.

+ References

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-Name Accounting Standards Codification
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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.

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-Publisher FASB
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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.

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

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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.

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