Risk Management Activities and Fair Value Measurements - Notional Amounts and Fair Values of Qualifying and Non-Qualifying Financial Instruments used in Hedging Transactions (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Jun. 30, 2011
Derivatives in Cash Flow Hedging Relationships
Notional amount	$ 858	$ 847
Fair Value Asset (Liability)	(168)	(114)
Derivatives in Cash Flow Hedging Relationships | Interest Rate
Notional amount	0	0
Fair Value Asset (Liability)	0	0
Derivatives in Cash Flow Hedging Relationships | Foreign currency hedges
Notional amount	831	831
Fair Value Asset (Liability)	(169)	(118)
Derivatives in Cash Flow Hedging Relationships | Commodities
Notional amount	27	16
Fair Value Asset (Liability)	1	4
Derivatives in Fair Value Hedging Relationships | Interest Rate
Notional amount	8,852	10,308
Fair Value Asset (Liability)	275	163
Derivatives in Net Investment Hedging Relationships
Notional amount	1,809	1,540
Fair Value Asset (Liability)	(64)	(138)
Derivatives Not Designated as Hedging Instruments
Notional amount	13,827	14,996
Fair Value Asset (Liability)	(242)	138
Derivatives Not Designated as Hedging Instruments | Foreign currency hedges
Notional amount	13,811	14,957
Fair Value Asset (Liability)	(242)	139
Derivatives Not Designated as Hedging Instruments | Commodities
Notional amount	16	39
Fair Value Asset (Liability)	$ 0	$ (1)