Debt - Extinguishments of Debt (Details) - USD ($) $ in Millions	Sep. 30, 2019	Jun. 30, 2019	Jun. 30, 2018	Mar. 31, 2018
Extinguishment of Debt [Line Items]
Debt Instrument, Repurchased Face Amount		$ 1,100	$ 539	$ 461
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