Capital Leases - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Mar. 31, 2018
Leases [Abstract]
Capital lease assets, net	$ 314		$ 314		$ 274
Capital lease, accumulated depreciation	83		83		57
Depreciation of capital lease assets	25	$ 15	47	$ 30
Capital lease obligations	301		301		$ 304
Interest expense on capital leases	$ 5	$ 5	$ 9	$ 7

Amount equal to the present value (the principal) at the beginning of the lease term of minimum lease payments during the lease term (excluding that portion of the payments representing executory costs such as insurance, maintenance, and taxes to be paid by the lessor, together with any profit thereon) net of payments or other amounts applied to the principal through the balance sheet date.

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-Name Accounting Standards Codification
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-SubTopic 10
-Section S99
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- Definition

The total gross amount less the charge for the use of the long-lived depreciable assets subject to a lease meeting the criteria for capitalization.

+ References

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-Publisher FASB
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- Definition

The charge for the use of long-lived depreciable capital leased assets for the period.

+ References

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The financing charge for leasing arrangements meeting the criteria for capitalization.

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The total charge for the use of long-lived depreciable assets subject to a lease meeting the criteria for capitalization.

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