Risk Management Activities and Fair Value Measurements - Derivative Notional Amounts and Fair Value (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Jun. 30, 2012
Cash Flow Hedging [Member]
Derivative [Line Items]
Notional amount	$ 951	$ 831
Fair Value Asset (Liability)	140	(142)
Cash Flow Hedging [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Notional amount	0	0
Fair Value Asset (Liability)	0	0
Cash Flow Hedging [Member] | Foreign Exchange Contract [Member]
Derivative [Line Items]
Notional amount	951	831
Fair Value Asset (Liability)	140	(142)
Fair Value Hedging [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Notional amount	9,057	10,747
Fair Value Asset (Liability)	260	298
Net Investment Hedging [Member]
Derivative [Line Items]
Notional amount	1,688	1,768
Fair Value Asset (Liability)	251	13
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional amount	9,228	13,335
Fair Value Asset (Liability)	(56)	64
Not Designated as Hedging Instrument [Member] | Foreign Exchange Contract [Member]
Derivative [Line Items]
Notional amount	9,204	13,210
Fair Value Asset (Liability)	(55)	63
Not Designated as Hedging Instrument [Member] | Commodity Contract [Member]
Derivative [Line Items]
Notional amount	24	125
Fair Value Asset (Liability)	$ (1)	$ 1