Investments - Schedule of Total Gains and Losses on Equity Securities (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2020	Dec. 31, 2019
Schedule of Investments [Abstract]
Total gains (losses) recognized on equity securities	$ 33	$ (6)	$ 42	$ (5)
Less: Net gains recognized on equity securities sold	0	0	0	0
Unrealized gains (losses) recognized on equity securities held at end of period	$ 33	$ (6)	$ 42	$ (5)