Share-Based Payments - Narrative (Details) $ / shares in Units, $ in Thousands, shares in Millions			12 Months Ended
	May 21, 2025	Sep. 30, 2024 shares	Dec. 31, 2025 USD ($) incentiveProgram $ / shares shares	Dec. 31, 2024 USD ($) $ / shares	Dec. 31, 2023 USD ($) $ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation			$ 79,719	$ 79,429	$ 83,334
Income tax benefits from share-based payment arrangements			9,000	$ 9,000	$ 10,000
Total unrecognized compensation cost related to unvested share-based payments			$ 114,000
Weighted average period for unrecognized compensation cost expected to be recognized			2 years 1 month 6 days
Weighted average grant date fair value of stock options granted (USD per share) | $ / shares			$ 0	$ 0	$ 8.91
Intrinsic value of stock options exercised			$ 5,000	$ 2,000	$ 9,000
Intrinsic value of stock options outstanding			$ 24,000
Weighted average remaining life of stock options outstanding			3 years
Intrinsic value of stock options exercisable			$ 23,000
Weighted average remaining life of stock options exercisable			2 years 10 months 24 days
Cash received from stock options exercised			$ 9,803	6,345	26,742
Stock options vested or expected to vest (in shares) | shares			8.0
Intrinsic value of stock options vested or expected to vest			$ 24,000
Weighted average exercise price of stock options vested or expected to vest (USD per share) | $ / shares			$ 19.32
Weighted average remaining life of stock options vested or expected to vest			3 years
Approximate stock options vested (in shares) | shares			1.0
Approximate total grant date fair value of stock options vested			$ 3,000	6,000	9,000
Weighted average grant date fair value of restricted stock units expected to vest (USD per share) | $ / shares			$ 17.95
Number of long-term incentive programs | incentiveProgram			4
Retention Performance Grant, Stock Hurdle Price
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
General vesting period		5 years
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation			$ 1,700	3,100	6,700
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
General vesting period			3 years
Share-based compensation			$ 56,700	55,200	48,500
Stock units expected to vest (in shares) | shares			6.0
Total grant date fair value of restricted stock units vested			$ 56,000	$ 49,000	$ 42,000
Weighted average grant date fair value (USD per share) | $ / shares			$ 17.57	$ 18.50	$ 18.24
Performance Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation			$ 21,300	$ 21,200	$ 28,100
Stock units expected to vest (in shares) | shares			2.0
Weighted average grant date fair value of restricted stock units expected to vest (USD per share) | $ / shares			$ 21.41
Total grant date fair value of restricted stock units vested			$ 8,000	$ 18,000	$ 26,000
Weighted average grant date fair value (USD per share) | $ / shares			$ 26.43	$ 21.97	$ 19.44
Performance Awards | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Long-term incentive program, percentage of shares that may ultimately be earned			200.00%
Performance Awards | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Long-term incentive program, percentage of shares that may ultimately be earned			0.00%
Retention Performance Grant
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
General vesting period		5 years
Remaining number of shares of common stock available for grant under the Mattel, Inc. 2010 Equity and Long-Term Compensation Plan (in shares) | shares		0.8
Long-term incentive program, percentage of shares that may ultimately be earned		100.00%
Target value			$ 15,000
Retention Performance Grant | Retention Performance Grant, Stock Hurdle Price
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
General vesting period		3 years
Long-term incentive program, percentage of shares that may ultimately be earned		50.00%
Retention Performance Grant | Retention Performance Grant, TSR
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
General vesting period		5 years
Long-term incentive program, percentage of shares that may ultimately be earned		50.00%
Retention Performance Grant | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Long-term incentive program, percentage of shares that may ultimately be earned		200.00%
Amended 2010 Plan | Prior To April 28, 2023
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Age requirement for accelerated vesting			55
Service period requirement for accelerated vesting			5 years
Amended 2010 Plan | On Or After April 28, 2023
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Age requirement for accelerated vesting			55
Service period requirement for accelerated vesting			10 years
Amended 2010 Plan | Target Performance Goals
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Remaining number of shares of common stock available for grant under the Mattel, Inc. 2010 Equity and Long-Term Compensation Plan (in shares) | shares			23.0
Amended 2010 Plan | Maximum Achievement Goals
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Remaining number of shares of common stock available for grant under the Mattel, Inc. 2010 Equity and Long-Term Compensation Plan (in shares) | shares			19.0
Amended 2010 Plan | Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Minimum grant date fair value of nonqualified stock options as a percentage of the fair value of Mattel's common stock			100.00%
General vesting period			3 years
Accelerated vesting period for individuals who meet the age and service requirements			6 months
Exercise period after termination			90 days
Amended 2010 Plan | Stock Options | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option expire from date of grant, period (no later than)			10 years
Amended 2010 Plan | Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
General vesting period			3 years
Accelerated vesting period for individuals who meet the age and service requirements			6 months
Amended 2010 Plan | Performance Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Accelerated vesting period for individuals who meet the age and service requirements			6 months
LTIP 2025
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance period	3 years
LTIP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance period	3 years