Summary of Changes in Accumulated Other Comprehensive Income (Loss) by Component (Parenthetical) (Detail) - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Dec. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2017 |
Dec. 31, 2016 |
|
| Derivatives | ||||
| Accumulated Other Comprehensive Income (Loss) [Line Items] | ||||
| Unrealized gains (losses), tax | $ 1 | $ 3 | $ 1 | $ 4 |
| Net change related to other comprehensive income (loss), tax | 0 | 0 | (1) | (2) |
| Investments | ||||
| Accumulated Other Comprehensive Income (Loss) [Line Items] | ||||
| Unrealized gains (losses), tax | (211) | (292) | (161) | (110) |
| Net change related to other comprehensive income (loss), tax | (474) | (535) | (618) | (491) |
| Translation adjustments and other | ||||
| Accumulated Other Comprehensive Income (Loss) [Line Items] | ||||
| Net change related to other comprehensive income (loss), tax | $ 0 | $ 0 | $ (1) | $ 7 |