Acquisitions, Disposals and Other Transactions (Details)	12 Months Ended
	Jun. 30, 2026 USD ($) business	Jun. 30, 2025 USD ($) business	Jun. 30, 2024 USD ($) business	Jun. 14, 2026 USD ($) $ / shares	Jan. 12, 2024
Business Combination [Line Items]
Number of businesses acquired | business	0	2	0
Deconsolidation, gain, amount	$ 0	$ 0	$ 166,000,000
Disposal | United States Football League
Business Combination [Line Items]
Deconsolidation, gain, amount			$ 170,000,000
United States Football League
Business Combination [Line Items]
Equity method investment, ownership percentage					42.00%
Term Loan Agreement | Line of Credit | Secured Debt
Business Combination [Line Items]
Debt instrument, face amount	1,000,000,000.0
Roku TV Streaming Platform
Business Combination [Line Items]
Business combination, consideration transferred, equity interests issued and issuable, cash paid per acquiree share (in dollars per share) | $ / shares				$ 96.00
Business combination, consideration transferred, equity interests issued and issuable, entity shares issued per acquiree share (in dollars per share) | $ / shares				$ 0.9693
Business combination, termination fee payable upon change in board recommendation				$ 866,000,000
Business combination, termination fee payable upon failure to obtain approval				1,200,000,000
Business combination, third party cost reimbursement payable upon failure to obtain approval				$ 70,000,000
Roku TV Streaming Platform | Fully Committed Bridge Financing
Business Combination [Line Items]
Debt instrument, face amount	12,000,000,000.0
Roku TV Streaming Platform | Senior Unsecured Bridge Facility | Bridge Loan
Business Combination [Line Items]
Debt instrument, face amount	11,000,000,000.0
Roku TV Streaming Platform | Term Loan Agreement | Line of Credit | Secured Debt
Business Combination [Line Items]
Debt instrument, face amount	$ 1,000,000,000.0