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, 2013	Dec. 31, 2012	Sep. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Mar. 31, 2013	Mar. 31, 2012
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance, beginning of period	$ 23	$ 22	$ 14	$ 14	$ 60	$ 83	$ 14	$ 83
Realized and unrealized gains (losses):
Included in other income (expense)	0	0	0	0	(3)	(2)
Included in other comprehensive income (loss)	1	1	0	0	0	(21)
Purchases			8
Conversions of Level 3 instruments to Level 1 instruments					(43)
Balance, end of period	24	23	22	14	14	60	24	14
Change in unrealized gains (losses) included in other income (expense) related to assets held as of period end	0			0			0	0
Corporate notes and bonds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance, beginning of period	18	17	9	9	37	58	9	58
Realized and unrealized gains (losses):
Included in other income (expense)	0	0	0	0	0	0
Included in other comprehensive income (loss)	1	1	0	0	0	(21)
Purchases			8
Conversions of Level 3 instruments to Level 1 instruments					(28)
Balance, end of period	19	18	17	9	9	37	19	9
Change in unrealized gains (losses) included in other income (expense) related to assets held as of period end	0			0			0	0
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
Realized and unrealized gains (losses):
Included in other income (expense)	0	0	0	0	0	0
Included in other comprehensive income (loss)	0	0	0	0	0	0
Purchases			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	0	0	0	18	20	0	20
Realized and unrealized gains (losses):
Included in other income (expense)	0	0	0	0	(3)	(2)
Included in other comprehensive income (loss)	0	0	0	0	0	0
Purchases			0
Conversions of Level 3 instruments to Level 1 instruments					(15)
Balance, end of period	0	0	0	0	0	18	0	0
Change in unrealized gains (losses) included in other income (expense) related to assets held as of period end	$ 0			$ 0			$ 0	$ 0