Summary of Changes in Accumulated Other Comprehensive Income (Loss) by Component (Parenthetical) (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Derivatives
Accumulated Other Comprehensive Income (Loss) [Line Items]
Unrealized gains (losses), tax	$ 1	$ 3	$ 1	$ 4
Net change related to other comprehensive income (loss), tax	0	0	(1)	(2)
Investments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Unrealized gains (losses), tax	(211)	(292)	(161)	(110)
Net change related to other comprehensive income (loss), tax	(474)	(535)	(618)	(491)
Translation adjustments and other
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net change related to other comprehensive income (loss), tax	$ 0	$ 0	$ (1)	$ 7