Risk Management Activities and Fair Value Measurements - Derivative Notional Amounts and Fair Value (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Jun. 30, 2014
Cash Flow Hedging [Member] | Foreign Exchange Contract [Member]
Derivative [Line Items]
Derivative, Notional Amount	$ 951	$ 951
Derivative Assets (Liabilities), at Fair Value, Net	304	187
Fair Value Hedging [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Derivative, Notional Amount	7,139	9,738
Derivative Assets (Liabilities), at Fair Value, Net	276	168
Net Investment Hedging [Member]
Derivative [Line Items]
Derivative, Notional Amount	570	831
Derivative Assets (Liabilities), at Fair Value, Net	90	48
Not Designated as Hedging Instrument [Member] | Foreign Exchange Contract [Member]
Derivative [Line Items]
Derivative, Notional Amount	7,579	12,111
Derivative Assets (Liabilities), at Fair Value, Net	$ 26	$ (42)