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	Sep. 30, 2024	Jun. 30, 2024
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Amount	$ 19,558	$ 16,325
Fair Value Asset	36	120
Fair Value (Liability)	(562)	(379)
Designated as Hedging Instrument
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Amount	15,658	13,133
Fair Value Asset	0	119
Fair Value (Liability)	(559)	(356)
Interest rate contracts | Fair Value Hedging
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Amount	3,127	2,993
Fair Value Asset	0	0
Fair Value (Liability)	(249)	(325)
Foreign currency interest rate contracts | Not Designated as Hedging Instrument
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Amount	3,900	3,192
Fair Value Asset	36	1
Fair Value (Liability)	(3)	(23)
Foreign currency interest rate contracts | Net Investment Hedging
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Amount	12,531	10,140
Fair Value Asset	0	119
Fair Value (Liability)	$ (310)	$ (31)