Net Income per Common Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended				6 Months Ended
	Jan. 02, 2026	Oct. 03, 2025	Dec. 27, 2024	Sep. 27, 2024	Jan. 02, 2026	Dec. 27, 2024	Jun. 27, 2025	Feb. 21, 2025
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Shares issued (in shares)	148.0				148.0		146.0	145.0
Par value (in dollars per share)	$ 0.01				$ 0.01		$ 0.01	$ 0.01
Net Income (Loss)	$ 803	$ 112	$ 104	$ 211	$ 915	$ 315
Weighted average shares outstanding:
Basic (in shares)	147.0		145.0		146.0	145.0
Diluted (in shares)	156.0		145.0		152.0	145.0
Net income per common share:
Basic (in dollars per share)	$ 5.46		$ 0.72		$ 6.27	$ 2.17
Diluted (in dollars per share)	$ 5.15		$ 0.72		$ 6.02	$ 2.17
Antidilutive weighted-average shares (in shares)	0.1				0.1
Western Digital Corporation
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Percent distribution of shares								80.10%