Summary of Significant Accounting Policies - Argentina Operations (Details)	Dec. 31, 2020	Dec. 31, 2019
Argentina
Financial Statement Line Items with Differences in Reported Amount and Reporting Currency Denominated Amounts [Line Items]
Percentage of subsidiary net sales to Mattel's consolidated net sales (less than)	1.00%	1.00%

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

Name:	us-gaap_FinancialStatementLineItemsWithDifferencesInReportedAmountAndReportingCurrencyDenominatedAmountsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration