RISK MANAGEMENT ACTIVITIES AND FAIR VALUE MEASUREMENTS - ADDITIONAL INFORMATION (Details) - USD ($) $ in Millions	Sep. 30, 2015	Jun. 30, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long Term Debt, Current Maturities measured at Fair Value	$ 3,273	$ 2,776
Estimate of Fair Value Measurement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt, Fair Value	22,657	23,127
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt, Fair Value	2,184	2,180
US Treasury and Government [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Debt Maturities, Next Twelve Months, Amortized Cost Basis	550	700
Available-for-sale Securities, Debt Maturities, Year Two Through Five, Amortized Cost Basis	3,091	2,789
Corporate Bond Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Debt Maturities, Next Twelve Months, Amortized Cost Basis	267	221
Available-for-sale Securities, Debt Maturities, Year Two Through Five, Amortized Cost Basis	$ 980	$ 1,052