Income Taxes - Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at beginning of fiscal year	$ 52	$ 8	$ 8
Decrease for prior-year tax positions	(25)	0	0
Decrease for transfers to Parent	0	(2)	0
Increase for prior-year tax positions	12	45	0
Increase for current year tax positions	0	1	0
Balance at end of fiscal year	$ 39	$ 52	$ 8

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

No definition available.

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- Definition

Amount of unrecognized tax benefits.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 45
-Paragraph 10B
-URI http://asc.fasb.org/extlink&oid=116821951&loc=SL37586934-109318

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-Publisher FASB
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-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15A
-Subparagraph (a)
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- Definition

Amount of decrease in unrecognized tax benefits resulting from acquisitions.

+ References

No definition available.

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- Definition

Amount of decrease in unrecognized tax benefits resulting from tax positions taken in prior period tax returns.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
-Section 50
-Paragraph 15A
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- Definition

Amount of increase in unrecognized tax benefits resulting from tax positions that have been or will be taken in current period tax return.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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-SubTopic 10
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Amount of increase in unrecognized tax benefits resulting from tax positions taken in prior period tax returns.

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