Employee Benefit Plans - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Employee Benefits Disclosure [Line Items]
Accumulated benefit obligation of defined benefit pension plans	$ 408.8	$ 409.6
Discount rate	5.00%	5.30%
Total estimated cash contributions to be made during the next fiscal year for defined benefit pension and postretirement benefit plans	$ 14.0
Percentage limitation of an employee's total account balance that may be allocated to the Mattel Stock Fund in the Mattel, Inc. Personal Investment Plan	25.00%
Liability for deferred compensation and excess benefit plans	$ 60.9	$ 56.9
Cash surrender value of life insurance policies	109.7	97.1
Expense for incentive compensation plans	$ 83.4	$ 150.9	$ 137.8
Defined benefit pension plans
Employee Benefits Disclosure [Line Items]
Discount rate	5.00%	5.30%
Long-term rate of return on plan assets used to determine net periodic benefit cost for domestic defined benefit pension plans	6.20%	6.20%	5.00%