Stockholders' Equity (Other Comprehensive (Loss) Income) (Details) - USD ($) $ in Millions		12 Months Ended
		Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2019
Accumulated Other Comprehensive Income Loss [Line Items]
Other comprehensive income (loss), net of tax		$ 99	$ (109)	$ (89)
Benefit plan adjustments and other
Accumulated Other Comprehensive Income Loss [Line Items]
Unrealized gains (losses), before tax		87	(175)	(133)
Reclassifications realized in net income, before tax	[1]	45	29	12
Other comprehensive income (loss), before tax		132	(146)	(121)
Unrealized gains (losses),tax		(21)	44	35
Reclassifications realized in net income, tax	[1]	(12)	(7)	(3)
Other comprehensive income (loss), tax		(33)	37	32
Unrealized gains (losses), net of tax		66	(131)	(98)
Reclassifications realized in net income, net of tax	[1]	33	22	9
Other comprehensive income (loss), net of tax		$ 99	$ (109)	$ (89)

[1] Reclassifications of amounts related to benefit plan adjustments are included in Other, net in the Statements of Operations (See Note 15—Pension and Other Postretirement Benefits for additional information).