Net Recognized Gains (Losses) on Equity Investments (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
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	$ 30	$ 1,046	$ 233	$ 1,692
Net unrealized gains on investments still held	73	0	191	0
Total	94	768	337	1,341
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	(3)	(20)	(3)	(25)
Total	$ 100	$ 1,026	$ 421	$ 1,667