Net Recognized Gains (Losses) on Debt Investments (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 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	$ 6	$ 4	$ 19	$ 22
Realized losses from sales of available-for-sale securities	(10)	(334)	(100)	(673)
Total	44	510	381	1,851
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	0	(1)	(7)	(6)
Total	$ (4)	$ (331)	$ (88)	$ (657)