Financial Instruments Summary of Estimated Fair Value of Long-term Obligations and Other Short-term Borrowings (Details) - USD ($) $ in Millions	Dec. 31, 2018	Jun. 30, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying amount	$ 9,049	$ 9,013
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated fair value	$ 8,717	$ 8,852