Consolidated Balance Sheets (Parenthetical) - USD ($) shares in Millions, $ in Millions	Sep. 30, 2025	Jun. 30, 2025
Statement of Financial Position [Abstract]
Trade accounts receivable, net of allowances	$ 9	$ 10
Property, plant and equipment, net of accumulated depreciation	$ 4,528	$ 4,480
Serial preferred stock, par value (in USD per share)	$ 0.50	$ 0.50
Serial preferred stock, authorized (in shares)	3.0	3.0
Serial preferred stock, issued (in shares)	0.0	0.0
Common stock, par value (in USD per share)	$ 0.50	$ 0.50
Common stock, authorized (in shares)	600.0	600.0
Common stock, issued (in shares)	181.0	181.0
Treasury shares at cost (in shares)	54.9	54.4