Unrealized Loss Position Investments (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Jun. 30, 2013
Unrealized Losses on Investments [Line Items]
Less than 12 Months - Fair Value	$ 4,468	$ 5,506
Less than 12 Months - Unrealized Losses	(251)	(321)
12 Months or Greater - Fair Value	467	544
12 Months or Greater - Unrealized Losses	(25)	(139)
Total Fair Value	4,935	6,050
Total Unrealized Losses	(276)	(460)
U.S. government and agency securities
Unrealized Losses on Investments [Line Items]
Less than 12 Months - Fair Value	1,386	2,208
Less than 12 Months - Unrealized Losses	(53)	(84)
12 Months or Greater - Fair Value	242	0
12 Months or Greater - Unrealized Losses	(8)	0
Total Fair Value	1,628	2,208
Total Unrealized Losses	(61)	(84)
Foreign government bonds
Unrealized Losses on Investments [Line Items]
Less than 12 Months - Fair Value	870	589
Less than 12 Months - Unrealized Losses	(29)	(18)
12 Months or Greater - Fair Value	3	69
12 Months or Greater - Unrealized Losses	(1)	(23)
Total Fair Value	873	658
Total Unrealized Losses	(30)	(41)
Mortgage-backed securities
Unrealized Losses on Investments [Line Items]
Less than 12 Months - Fair Value	298	357
Less than 12 Months - Unrealized Losses	(9)	(12)
12 Months or Greater - Fair Value	55	39
12 Months or Greater - Unrealized Losses	(1)	(1)
Total Fair Value	353	396
Total Unrealized Losses	(10)	(13)
Corporate notes and bonds
Unrealized Losses on Investments [Line Items]
Less than 12 Months - Fair Value	944	1,142
Less than 12 Months - Unrealized Losses	(29)	(38)
12 Months or Greater - Fair Value	95	27
12 Months or Greater - Unrealized Losses	(4)	(2)
Total Fair Value	1,039	1,169
Total Unrealized Losses	(33)	(40)
Municipal securities
Unrealized Losses on Investments [Line Items]
Less than 12 Months - Fair Value	49	44
Less than 12 Months - Unrealized Losses	(2)	(1)
12 Months or Greater - Fair Value	0	0
12 Months or Greater - Unrealized Losses	0	0
Total Fair Value	49	44
Total Unrealized Losses	(2)	(1)
Common and preferred stock
Unrealized Losses on Investments [Line Items]
Less than 12 Months - Fair Value	921	1,166
Less than 12 Months - Unrealized Losses	(129)	(168)
12 Months or Greater - Fair Value	72	409
12 Months or Greater - Unrealized Losses	(11)	(113)
Total Fair Value	993	1,575
Total Unrealized Losses	$ (140)	$ (281)