Unrealized Loss Position Investments (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012	Jun. 30, 2011
Investments, Unrealized Loss Position [Line Items]
Less than 12 Months - Fair Value	$ 3,511	$ 3,118
Less than 12 Months - Unrealized Losses	(221)	(170)
12 Months or Greater - Fair Value	214	245
12 Months or Greater - Unrealized Losses	(26)	(49)
Total Fair Value	3,725	3,363
Total Unrealized Losses	(247)	(219)
U.S. government and agency securities
Investments, Unrealized Loss Position [Line Items]
Less than 12 Months - Fair Value	992	484
Less than 12 Months - Unrealized Losses	(19)	(7)
12 Months or Greater - Fair Value	0	0
12 Months or Greater - Unrealized Losses	0	0
Total Fair Value	992	484
Total Unrealized Losses	(19)	(7)
Foreign government bonds
Investments, Unrealized Loss Position [Line Items]
Less than 12 Months - Fair Value	328	365
Less than 12 Months - Unrealized Losses	(21)	(2)
12 Months or Greater - Fair Value	0	0
12 Months or Greater - Unrealized Losses	0	0
Total Fair Value	328	365
Total Unrealized Losses	(21)	(2)
Mortgage-backed securities
Investments, Unrealized Loss Position [Line Items]
Less than 12 Months - Fair Value	0	63
Less than 12 Months - Unrealized Losses	0	(3)
12 Months or Greater - Fair Value	51	14
12 Months or Greater - Unrealized Losses	(2)	(1)
Total Fair Value	51	77
Total Unrealized Losses	(2)	(4)
Corporate notes and bonds
Investments, Unrealized Loss Position [Line Items]
Less than 12 Months - Fair Value	582	750
Less than 12 Months - Unrealized Losses	(8)	(10)
12 Months or Greater - Fair Value	23	25
12 Months or Greater - Unrealized Losses	(1)	(1)
Total Fair Value	605	775
Total Unrealized Losses	(9)	(11)
Municipal securities
Investments, Unrealized Loss Position [Line Items]
Less than 12 Months - Fair Value	37	79
Less than 12 Months - Unrealized Losses	(1)	(2)
12 Months or Greater - Fair Value	0	0
12 Months or Greater - Unrealized Losses	0	0
Total Fair Value	37	79
Total Unrealized Losses	(1)	(2)
Common and preferred stock
Investments, Unrealized Loss Position [Line Items]
Less than 12 Months - Fair Value	1,572	1,377
Less than 12 Months - Unrealized Losses	(172)	(146)
12 Months or Greater - Fair Value	140	206
12 Months or Greater - Unrealized Losses	(23)	(47)
Total Fair Value	1,712	1,583
Total Unrealized Losses	$ (195)	$ (193)