Investments - Schedule of Total Gains and Losses on Equity Securities (Detail) - USD ($) $ in Millions	12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2018
Schedule of Investments [Abstract]
Total (losses) gains recognized on equity securities	$ (21)	$ (23)	$ 35
Less: Net (losses) gains recognized on equity securities sold or impaired	0	0	7
Unrealized (losses) gains recognized on equity securities held at end of period	$ (21)	$ (23)	$ 28