Risk Management Activities and Fair Value Measurements - Fair Value (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014	Jun. 30, 2014
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	$ 77	$ 39
Available-for-sale Securities, Debt Maturities, Rolling Year Two Through Five, Amortized Cost Basis	909	458
Liabilities, Fair Value Disclosure [Abstract]
Long Term Debt, Current Maturities measured at Fair Value	2,651	4,400
US Treasury and Government [Member]
Assets, Fair Value Disclosure [Abstract]
Investment securities	2,377	1,631
Other Investments [Member]
Assets, Fair Value Disclosure [Abstract]
Investment securities	33	30
Corporate Bond Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Investment securities	983	497
Fair Value Measurement [Domain]
Assets, Fair Value Disclosure [Abstract]
Investment securities	3,393	2,158
Fair Value, Inputs, Level 2 [Member]
Liabilities, Fair Value Disclosure [Abstract]
Long-term Debt, Fair Value	1,681	1,682
Estimate of Fair Value, Fair Value Disclosure [Member]
Liabilities, Fair Value Disclosure [Abstract]
Long-term Debt, Fair Value	23,992	26,429
Other Current Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Amortized Cost Basis	150	0
Other Noncurrent Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Amortized Cost Basis	$ 2,248	$ 1,649