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Net Recognized Gains (Losses) on Debt Investments (Detail) - USD ($)
$ in Millions
 12 Months Ended
Jun. 30, 2020
Jun. 30, 2019
Jun. 30, 2018
Schedule Of Gain Loss On Investments Including Marketable Securities And Investments Held At Cost Income Statement Reported Amounts Summary [Line Items]      
Realized gains from sales of available-for-sale securities $ 50 $ 12 $ 27
Realized losses from sales of available-for-sale securities (37) (93) (987)
Total 32 648 2,399
Debt Securities      
Schedule Of Gain Loss On Investments Including Marketable Securities And Investments Held At Cost Income Statement Reported Amounts Summary [Line Items]      
Other-than-temporary impairments of investments (17) (16) (6)
Total $ (4) $ (97) $ (966)