Financial Instruments (Summary of Estimated Fair Value of Long-term Obligations and Other Short-term Borrowings) (Details) - USD ($) $ in Millions	Jun. 30, 2018	Jun. 30, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying amount	$ 9,013	$ 10,395
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated fair value	$ 8,852	10,713
Interest Rate Swaps | Designated as Hedging Instrument | Fair Value Hedging
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, Hedge Discontinuances, Termination of Hedging Instrument, Amount		$ 600