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, 2016 |
Jun. 30, 2015 |
|---|---|---|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ||
| Investments, Fair Value Disclosure | $ 6,274 | $ 4,797 |
| US Government Debt Securities | ||
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ||
| Investments, Fair Value Disclosure | 4,839 | 3,495 |
| Corporate Bond Securities | ||
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ||
| Investments, Fair Value Disclosure | 1,407 | 1,272 |
| Other Investments | ||
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ||
| Investments, Fair Value Disclosure | $ 28 | $ 30 |