Licensed Content Assets - Schedule of Amortization Expense for Licensed Content Assets (Details) $ in Thousands	Dec. 31, 2020 USD ($)
Capitalized Licensed Content Costs [Abstract]
2021	$ 6,527
2022	1,338
2023	$ 42

Amortization expense of licensed content assets next twelve months.

No definition available.

Name:	roku_AmortizationExpenseOfLicensedContentAssetsNextTwelveMonths
Namespace Prefix:	roku_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant