Financing Arrangement (Senior Notes) (Details) - USD ($) $ in Millions		6 Months Ended
	Feb. 04, 2016	Sep. 30, 2021	Mar. 31, 2021		Feb. 11, 2021	Feb. 24, 2016
Debt Instrument [Line Items]
Proceeds from Issuance of Senior Long-term Debt	$ 395
Senior Notes, Noncurrent		$ 1,877	$ 1,876	[1]
Senior Notes		1,877	1,876
Proceeds from Debt, Net of Issuance Costs		1,478
2026 Notes
Debt Instrument [Line Items]
Long-term Debt		$ 400	400			$ 400
Debt Instrument, Interest Rate, Stated Percentage						4.80%
Debt Instrument, Maturity Date	Mar. 01, 2026
Effective interest rate						4.97%
Debt Instrument, Convertible, Remaining Discount Amortization Period		4 years 4 months 24 days
Senior Notes
Debt Instrument [Line Items]
Long-term Debt		$ 1,900	1,900
Debt Instrument, Unamortized Discount (Premium), Net		(7)	(7)		$ 6	$ (1)
Debt Issuance Costs, Noncurrent, Net		(16)	(17)		16	$ (4)
Senior Notes, Frequency of Periodic Payment	semiannually
Debt Instrument, Fair Value Disclosure		$ 1,911	1,873
Debt Instrument, Redemption Price, Percentage		100.00%
Change of control repurchase event
Debt Instrument [Line Items]
Debt Instrument, Redemption Price, Percentage		101.00%
2031 Notes
Debt Instrument [Line Items]
Long-term Debt		$ 750	750		$ 750
Debt Instrument, Interest Rate, Stated Percentage					1.85%
Debt Instrument, Maturity Date		Feb. 15, 2031
Effective interest rate					1.98%
Debt Instrument, Convertible, Remaining Discount Amortization Period		9 years 4 months 24 days
2051 Notes
Debt Instrument [Line Items]
Long-term Debt		$ 750	$ 750		$ 750
Debt Instrument, Interest Rate, Stated Percentage					2.95%
Debt Instrument, Maturity Date		Feb. 15, 2051
Effective interest rate					3.04%
Debt Instrument, Convertible, Remaining Discount Amortization Period		29 years 4 months 24 days

[1] Derived from audited Consolidated Financial Statements.