Investments in Subsidiaries - Summary of Principal Subsidiaries (Details)	12 Months Ended
Dec. 31, 2025
Cereal Base CEBA AB \| Direct Ownership
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Name	Cereal Base CEBA AB
Country/place of registration and operations	Sweden
Principal activities	Holding
Proportion of voting rights and shares held (directly or indirectly) (%)	100.00%
Oatly AB \| Direct Ownership
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Name	Oatly AB
Country/place of registration and operations	Sweden
Principal activities	Holding
Proportion of voting rights and shares held (directly or indirectly) (%)	100.00%
Oatly Sweden Operations & Supply AB \| Indirect Ownership
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Name	Oatly Sweden Operations & Supply AB
Country/place of registration and operations	Sweden
Principal activities	Production
Proportion of voting rights and shares held (directly or indirectly) (%)	100.00%
Havrekärnan AB \| Indirect Ownership
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Name	Havrekärnan AB
Country/place of registration and operations	Sweden
Principal activities	Production
Proportion of voting rights and shares held (directly or indirectly) (%)	100.00%
Oatly UK Ltd \| Indirect Ownership
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Name	Oatly UK Ltd.
Country/place of registration and operations	United Kingdom
Principal activities	Selling
Proportion of voting rights and shares held (directly or indirectly) (%)	100.00%
Oatly Germany GmbH \| Indirect Ownership
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Name	Oatly Germany GmbH
Country/place of registration and operations	Germany
Principal activities	Selling
Proportion of voting rights and shares held (directly or indirectly) (%)	100.00%
Oatly Switzerland AG \| Indirect Ownership
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Name	Oatly Switzerland AG
Country/place of registration and operations	Switzerland
Principal activities	Selling
Proportion of voting rights and shares held (directly or indirectly) (%)	100.00%
Oatly Austria GmbH \| Indirect Ownership
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Name	Oatly Austria GmbH
Country/place of registration and operations	Austria
Principal activities	Selling
Proportion of voting rights and shares held (directly or indirectly) (%)	100.00%
Oatly Netherlands BV \| Indirect Ownership
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Name	Oatly Netherlands BV
Country/place of registration and operations	Netherlands
Principal activities	Selling
Proportion of voting rights and shares held (directly or indirectly) (%)	100.00%
Oatly Netherlands Operation & Supply BV \| Indirect Ownership
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Name	Oatly Netherlands Operation & Supply BV
Country/place of registration and operations	Netherlands
Principal activities	Production
Proportion of voting rights and shares held (directly or indirectly) (%)	100.00%
Oatly EMEA AB \| Indirect Ownership
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Name	Oatly EMEA AB
Country/place of registration and operations	Sweden
Principal activities	Selling
Proportion of voting rights and shares held (directly or indirectly) (%)	100.00%
Oatly Inc \| Indirect Ownership
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Name	Oatly Inc.
Country/place of registration and operations	United States
Principal activities	Holding
Proportion of voting rights and shares held (directly or indirectly) (%)	100.00%
Oatly US Inc \| Indirect Ownership
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Name	Oatly US Inc.
Country/place of registration and operations	United States
Principal activities	Selling
Proportion of voting rights and shares held (directly or indirectly) (%)	100.00%
Oatly US Operations & Supply Inc \| Indirect Ownership
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Name	Oatly US Operations & Supply Inc.
Country/place of registration and operations	United States
Principal activities	Production
Proportion of voting rights and shares held (directly or indirectly) (%)	100.00%
Oatly Shanghai Co. Ltd. \| Indirect Ownership
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Name	Oatly Shanghai Co. Ltd.
Country/place of registration and operations	China
Principal activities	Selling
Proportion of voting rights and shares held (directly or indirectly) (%)	100.00%
Dong Plant (Zhuhai) Food and Beverage Co., Ldt \| Indirect Ownership
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Name	Dong Plant (Zhuhai) Food and Beverage Co., Ldt
Country/place of registration and operations	China
Principal activities	Selling
Proportion of voting rights and shares held (directly or indirectly) (%)	100.00%
Oatly Food Co Ltd \| Indirect Ownership
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Name	Oatly Food Co Ltd.
Country/place of registration and operations	China
Principal activities	Production
Proportion of voting rights and shares held (directly or indirectly) (%)	100.00%