Risk Management Activities and Fair Value Measurements - Notional Amounts And Fair Values Of Qualifying And Non-Qualifying Financial Instruments Used In Hedging Transactions (Details) - USD ($) $ in Millions	Mar. 31, 2025	Jun. 30, 2024
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Amount	$ 19,149	$ 16,325
Fair Value Asset	84	120
Fair Value (Liability)	(347)	(379)
Designated as Hedging Instrument
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Amount	15,691	13,133
Fair Value Asset	78	119
Fair Value (Liability)	(340)	(356)
Interest rate contracts | Fair Value Hedging
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Amount	3,034	2,993
Fair Value Asset	0	0
Fair Value (Liability)	(217)	(325)
Foreign currency interest rate contracts | Not Designated as Hedging Instrument
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Amount	3,458	3,192
Fair Value Asset	6	1
Fair Value (Liability)	(7)	(23)
Foreign currency interest rate contracts | Net Investment Hedging
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Amount	12,657	10,140
Fair Value Asset	78	119
Fair Value (Liability)	$ (124)	$ (31)