Changes in Financial Instruments Measured at Level 3 Fair Value on Recurring Basis (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended						9 Months Ended
	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Mar. 31, 2012	Mar. 31, 2011
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance, beginning of period	$ 14	$ 60	$ 83	$ 191	$ 188	$ 181	$ 83	$ 181
Total realized and unrealized gains (losses):
Included in other income (expense)	0	(3)	(2)	33	1	9
Included in other comprehensive income	0	0	(21)	(55)	2	(2)
Purchases, issuances and settlements				(85)
Conversions of Level 3 instruments to Level 1 instruments		(43)
Balance, end of period	14	14	60	84	191	188	14	84
Change in unrealized gains (losses) included in other income (expense) related to assets held as of period end	0			0			0	10
Corporate notes and bonds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance, beginning of period	9	37	58	171	167	167	58	167
Total realized and unrealized gains (losses):
Included in other income (expense)	0	0	0	34	2	2
Included in other comprehensive income	0	0	(21)	(55)	2	(2)
Purchases, issuances and settlements				(85)
Conversions of Level 3 instruments to Level 1 instruments		(28)
Balance, end of period	9	9	37	65	171	167	9	65
Change in unrealized gains (losses) included in other income (expense) related to assets held as of period end	0			1			0	5
Common and preferred stock
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance, beginning of period	5	5	5	5	5	5	5	5
Total realized and unrealized gains (losses):
Included in other income (expense)	0	0	0	0	0	0
Included in other comprehensive income	0	0	0	0	0	0
Purchases, issuances and settlements				0
Conversions of Level 3 instruments to Level 1 instruments		0
Balance, end of period	5	5	5	5	5	5	5	5
Change in unrealized gains (losses) included in other income (expense) related to assets held as of period end	0			0			0	0
Derivative assets
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance, beginning of period	0	18	20	15	16	9	20	9
Total realized and unrealized gains (losses):
Included in other income (expense)	0	(3)	(2)	(1)	(1)	7
Included in other comprehensive income	0	0	0	0	0	0
Purchases, issuances and settlements				0
Conversions of Level 3 instruments to Level 1 instruments		(15)
Balance, end of period	0	0	18	14	15	16	0	14
Change in unrealized gains (losses) included in other income (expense) related to assets held as of period end	$ 0			$ (1)			$ 0	$ 5