Investments - Schedule of Total Gains and Losses on Equity Securities (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018
Schedule of Investments [Abstract]
Total losses recognized on equity securities	$ (6)	$ (44)	$ (5)	$ (29)
Less: Net gains recognized on equity securities sold	0	0	0	0
Unrealized losses recognized on equity securities held at end of period	$ (6)	$ (44)	$ (5)	$ (29)