Net Recognized Gains (Losses) on Investments (Detail) - USD ($) $ in Millions |
12 Months Ended | ||
|---|---|---|---|
Jun. 30, 2018 |
Jun. 30, 2017 |
Jun. 30, 2016 |
|
| Other Income And Expenses [Abstract] | |||
| Other-than-temporary impairments of investments | $ (47) | $ (55) | $ (322) |
| Realized gains from sales of available-for-sale securities | 3,478 | 3,064 | 1,376 |
| Realized losses from sales of available-for-sale securities | (1,032) | (426) | (386) |
| Total | $ 2,399 | $ 2,583 | $ 668 |