Debt - Extinguishments of Debt (Details) - USD ($) $ in Millions	Sep. 30, 2020	Jun. 30, 2020	Jun. 30, 2019
Extinguishment of Debt [Line Items]
Debt Instrument, Repurchased Face Amount	$ 950		$ 1,100
3.700% Notes due June 6, 2027
Extinguishment of Debt [Line Items]
Interest rate	3.70%	3.70%
Debt Instrument, Repurchased Face Amount			675
Notes 5.000% due November 12, 2040
Extinguishment of Debt [Line Items]
Interest rate		5.00%
Debt Instrument, Repurchased Face Amount			175
4.875% Notes due May 15, 2044
Extinguishment of Debt [Line Items]
Interest rate	4.875%	4.875%
Debt Instrument, Repurchased Face Amount			75
4.685% Notes due December 15, 2044
Extinguishment of Debt [Line Items]
Interest rate	4.685%	4.685%
Debt Instrument, Repurchased Face Amount			$ 175