RISK MANAGEMENT ACTIVITIES AND FAIR VALUE MEASUREMENTS - FINANCIAL ASSETS AND LIABILITIES MEASURED AT FAIR VALUE ON A RECURRING BASIS (Details) - USD ($) $ in Millions	Jun. 30, 2019	Jun. 30, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	$ 6,217	$ 9,422
US Government Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	3,648	5,544
Corporate Bond Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	2,400	3,737
Other Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	$ 169	$ 141