Unrealized Losses on Investments (Detail) - USD ($)
$ in Millions |
Mar. 31, 2016 |
Jun. 30, 2015 |
| Unrealized Losses on Investments [Line Items] |
|
|
| Less than 12 Months - Fair Value |
$ 39,767
|
$ 18,789
|
| Less than 12 Months - Unrealized Losses |
(231)
|
(236)
|
| 12 Months or Greater - Fair Value |
1,584
|
719
|
| 12 Months or Greater - Unrealized Losses |
(142)
|
(77)
|
| Total Fair Value |
41,351
|
19,508
|
| Total Unrealized Losses |
(373)
|
(313)
|
| U.S. government and agency securities |
|
|
| Unrealized Losses on Investments [Line Items] |
|
|
| Less than 12 Months - Fair Value |
29,389
|
6,636
|
| Less than 12 Months - Unrealized Losses |
(12)
|
(9)
|
| 12 Months or Greater - Fair Value |
529
|
421
|
| 12 Months or Greater - Unrealized Losses |
(11)
|
(21)
|
| Total Fair Value |
29,918
|
7,057
|
| Total Unrealized Losses |
(23)
|
(30)
|
| Foreign government bonds |
|
|
| Unrealized Losses on Investments [Line Items] |
|
|
| Less than 12 Months - Fair Value |
4,231
|
4,611
|
| Less than 12 Months - Unrealized Losses |
(2)
|
(12)
|
| 12 Months or Greater - Fair Value |
58
|
18
|
| 12 Months or Greater - Unrealized Losses |
(26)
|
(12)
|
| Total Fair Value |
4,289
|
4,629
|
| Total Unrealized Losses |
(28)
|
(24)
|
| Mortgage- and asset-backed securities |
|
|
| Unrealized Losses on Investments [Line Items] |
|
|
| Less than 12 Months - Fair Value |
2,403
|
3,171
|
| Less than 12 Months - Unrealized Losses |
(4)
|
(5)
|
| 12 Months or Greater - Fair Value |
136
|
28
|
| 12 Months or Greater - Unrealized Losses |
0
|
(1)
|
| Total Fair Value |
2,539
|
3,199
|
| Total Unrealized Losses |
(4)
|
(6)
|
| Corporate notes and bonds |
|
|
| Unrealized Losses on Investments [Line Items] |
|
|
| Less than 12 Months - Fair Value |
2,753
|
2,946
|
| Less than 12 Months - Unrealized Losses |
(34)
|
(29)
|
| 12 Months or Greater - Fair Value |
467
|
104
|
| 12 Months or Greater - Unrealized Losses |
(30)
|
(8)
|
| Total Fair Value |
3,220
|
3,050
|
| Total Unrealized Losses |
(64)
|
(37)
|
| Municipal securities |
|
|
| Unrealized Losses on Investments [Line Items] |
|
|
| Less than 12 Months - Fair Value |
|
36
|
| Less than 12 Months - Unrealized Losses |
|
(1)
|
| 12 Months or Greater - Fair Value |
|
0
|
| 12 Months or Greater - Unrealized Losses |
|
0
|
| Total Fair Value |
|
36
|
| Total Unrealized Losses |
|
(1)
|
| Common and preferred stock |
|
|
| Unrealized Losses on Investments [Line Items] |
|
|
| Less than 12 Months - Fair Value |
991
|
1,389
|
| Less than 12 Months - Unrealized Losses |
(179)
|
(180)
|
| 12 Months or Greater - Fair Value |
394
|
148
|
| 12 Months or Greater - Unrealized Losses |
(75)
|
(35)
|
| Total Fair Value |
1,385
|
1,537
|
| Total Unrealized Losses |
$ (254)
|
$ (215)
|