Summary of Significant Accounting Policies (Foreign Currency Translation) (Details) - USD ($) $ in Millions	12 Months Ended
Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2019
Derivative [Line Items]
Net gain (loss) on foreign currency forward contracts	$ (19)	$ (4)	$ 50
Net gain (loss) on foreign currency transactions	$ 9	$ 11	$ (9)

Amount before tax of foreign currency transaction realized and unrealized gain (loss) recognized in the income statement.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 830
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=125521441&loc=d3e30690-110894

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 830
-SubTopic 20
-Section 35
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=123602790&loc=d3e30226-110892

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 830
-SubTopic 10
-Section 45
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=120253306&loc=d3e28228-110885

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 830
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=124440516&loc=d3e30840-110895

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