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Net Recognized Gains (Losses) on Equity Investments (Detail) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2019
Dec. 31, 2018
Schedule Of Gain Loss On Investments Including Marketable Securities And Investments Held At Cost Income Statement Reported Amounts Summary [Line Items]        
Net realized gains on investments sold $ 53 $ 30 $ 75 $ 233
Net unrealized gains on investments still held 111 73 55 191
Total 162 94 105 337
Equity 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 (9) (3) (31) (3)
Total $ 155 $ 100 $ 99 $ 421