v3.26.1
Fair Value Measurements - Schedule of Assumptions used in Pricing Model (Details) - Black-Scholes Option Pricing Model - Level 3
Mar. 31, 2026
Dec. 31, 2025
Interest Rate | January 2025 Warrants    
Fair Value, Assets Measured on Recurring Basis, Observable and Unobservable Input Reconciliation [Line Items]    
Warrants measurement input 0.0379 0.0367
Interest Rate | February 2025 Offering Warrants    
Fair Value, Assets Measured on Recurring Basis, Observable and Unobservable Input Reconciliation [Line Items]    
Warrants measurement input 0.0379 0.0367
Interest Rate | July 2024 Private Placement Warrants    
Fair Value, Assets Measured on Recurring Basis, Observable and Unobservable Input Reconciliation [Line Items]    
Warrants measurement input 0.0375 0.036
Interest Rate | November 2025 Private Placement Warrants    
Fair Value, Assets Measured on Recurring Basis, Observable and Unobservable Input Reconciliation [Line Items]    
Warrants measurement input 0.039 0.0373
Interest Rate | Inducement Warrants    
Fair Value, Assets Measured on Recurring Basis, Observable and Unobservable Input Reconciliation [Line Items]    
Warrants measurement input 0.0387  
Interest Rate | Public Offering Warrants    
Fair Value, Assets Measured on Recurring Basis, Observable and Unobservable Input Reconciliation [Line Items]    
Warrants measurement input 0.0375 0.036
Interest Rate | Legacy Allurion Other Common Stock    
Fair Value, Assets Measured on Recurring Basis, Observable and Unobservable Input Reconciliation [Line Items]    
Warrants measurement input 0.0347 0.0347
Interest Rate | Legacy Allurion Series C Preferred Stock Warrants    
Fair Value, Assets Measured on Recurring Basis, Observable and Unobservable Input Reconciliation [Line Items]    
Warrants measurement input 0.0376 0.0376
Interest Rate | Legacy Allurion Series D-1 Preferred Stock Warrants | Minimum    
Fair Value, Assets Measured on Recurring Basis, Observable and Unobservable Input Reconciliation [Line Items]    
Warrants measurement input 0.0376 0.0376
Interest Rate | Legacy Allurion Series D-1 Preferred Stock Warrants | Maximum    
Fair Value, Assets Measured on Recurring Basis, Observable and Unobservable Input Reconciliation [Line Items]    
Warrants measurement input 0.0391 0.0391
Exercise Price | January 2025 Warrants    
Fair Value, Assets Measured on Recurring Basis, Observable and Unobservable Input Reconciliation [Line Items]    
Warrants measurement input 0.06 0.06
Exercise Price | February 2025 Offering Warrants    
Fair Value, Assets Measured on Recurring Basis, Observable and Unobservable Input Reconciliation [Line Items]    
Warrants measurement input 0.0523 0.0523
Exercise Price | July 2024 Private Placement Warrants    
Fair Value, Assets Measured on Recurring Basis, Observable and Unobservable Input Reconciliation [Line Items]    
Warrants measurement input 0.30 0.30
Exercise Price | November 2025 Private Placement Warrants    
Fair Value, Assets Measured on Recurring Basis, Observable and Unobservable Input Reconciliation [Line Items]    
Warrants measurement input 0.0167 0.0167
Exercise Price | Inducement Warrants    
Fair Value, Assets Measured on Recurring Basis, Observable and Unobservable Input Reconciliation [Line Items]    
Warrants measurement input 0.0115  
Exercise Price | Public Offering Warrants | Minimum    
Fair Value, Assets Measured on Recurring Basis, Observable and Unobservable Input Reconciliation [Line Items]    
Warrants measurement input 0.06 0.06
Exercise Price | Public Offering Warrants | Maximum    
Fair Value, Assets Measured on Recurring Basis, Observable and Unobservable Input Reconciliation [Line Items]    
Warrants measurement input 0.30 0.30
Exercise Price | Legacy Allurion Other Common Stock    
Fair Value, Assets Measured on Recurring Basis, Observable and Unobservable Input Reconciliation [Line Items]    
Warrants measurement input 0.2625 0.2625
Exercise Price | Legacy Allurion Series C Preferred Stock Warrants    
Fair Value, Assets Measured on Recurring Basis, Observable and Unobservable Input Reconciliation [Line Items]    
Warrants measurement input 1.6825 1.6825
Exercise Price | Legacy Allurion Series D-1 Preferred Stock Warrants    
Fair Value, Assets Measured on Recurring Basis, Observable and Unobservable Input Reconciliation [Line Items]    
Warrants measurement input 3.035 3.035
Estimated Fair Value of Underlying Share Price | January 2025 Warrants    
Fair Value, Assets Measured on Recurring Basis, Observable and Unobservable Input Reconciliation [Line Items]    
Warrants measurement input 0.0068 0.0123
Estimated Fair Value of Underlying Share Price | February 2025 Offering Warrants    
Fair Value, Assets Measured on Recurring Basis, Observable and Unobservable Input Reconciliation [Line Items]    
Warrants measurement input 0.0068 0.0123
Estimated Fair Value of Underlying Share Price | July 2024 Private Placement Warrants    
Fair Value, Assets Measured on Recurring Basis, Observable and Unobservable Input Reconciliation [Line Items]    
Warrants measurement input 0.0068 0.0123
Estimated Fair Value of Underlying Share Price | November 2025 Private Placement Warrants    
Fair Value, Assets Measured on Recurring Basis, Observable and Unobservable Input Reconciliation [Line Items]    
Warrants measurement input 0.0068 0.0123
Estimated Fair Value of Underlying Share Price | Inducement Warrants    
Fair Value, Assets Measured on Recurring Basis, Observable and Unobservable Input Reconciliation [Line Items]    
Warrants measurement input 0.0068  
Estimated Fair Value of Underlying Share Price | Public Offering Warrants    
Fair Value, Assets Measured on Recurring Basis, Observable and Unobservable Input Reconciliation [Line Items]    
Warrants measurement input 0.0068 0.0123
Estimated Fair Value of Underlying Share Price | Legacy Allurion Other Common Stock    
Fair Value, Assets Measured on Recurring Basis, Observable and Unobservable Input Reconciliation [Line Items]    
Warrants measurement input 0.0068 0.0123
Estimated Fair Value of Underlying Share Price | Legacy Allurion Series C Preferred Stock Warrants    
Fair Value, Assets Measured on Recurring Basis, Observable and Unobservable Input Reconciliation [Line Items]    
Warrants measurement input 0.0068 0.0123
Estimated Fair Value of Underlying Share Price | Legacy Allurion Series D-1 Preferred Stock Warrants    
Fair Value, Assets Measured on Recurring Basis, Observable and Unobservable Input Reconciliation [Line Items]    
Warrants measurement input 0.0068 0.0123
Expected Volatility | January 2025 Warrants    
Fair Value, Assets Measured on Recurring Basis, Observable and Unobservable Input Reconciliation [Line Items]    
Warrants measurement input 1.30 1.10
Expected Volatility | February 2025 Offering Warrants    
Fair Value, Assets Measured on Recurring Basis, Observable and Unobservable Input Reconciliation [Line Items]    
Warrants measurement input 1.30 1.10
Expected Volatility | July 2024 Private Placement Warrants    
Fair Value, Assets Measured on Recurring Basis, Observable and Unobservable Input Reconciliation [Line Items]    
Warrants measurement input 1.45 1.20
Expected Volatility | November 2025 Private Placement Warrants    
Fair Value, Assets Measured on Recurring Basis, Observable and Unobservable Input Reconciliation [Line Items]    
Warrants measurement input 1.20 1.086
Expected Volatility | Inducement Warrants    
Fair Value, Assets Measured on Recurring Basis, Observable and Unobservable Input Reconciliation [Line Items]    
Warrants measurement input 1.15  
Expected Volatility | Public Offering Warrants    
Fair Value, Assets Measured on Recurring Basis, Observable and Unobservable Input Reconciliation [Line Items]    
Warrants measurement input 1.45 1.20
Expected Volatility | Legacy Allurion Other Common Stock    
Fair Value, Assets Measured on Recurring Basis, Observable and Unobservable Input Reconciliation [Line Items]    
Warrants measurement input 1.30 1.30
Expected Volatility | Legacy Allurion Series C Preferred Stock Warrants    
Fair Value, Assets Measured on Recurring Basis, Observable and Unobservable Input Reconciliation [Line Items]    
Warrants measurement input 1.069 1.069
Expected Volatility | Legacy Allurion Series D-1 Preferred Stock Warrants    
Fair Value, Assets Measured on Recurring Basis, Observable and Unobservable Input Reconciliation [Line Items]    
Warrants measurement input 1.069 1.069
Expected Life (Years) | January 2025 Warrants    
Fair Value, Assets Measured on Recurring Basis, Observable and Unobservable Input Reconciliation [Line Items]    
Warrants term 4 years 10 days 4 years 3 months 10 days
Expected Life (Years) | February 2025 Offering Warrants    
Fair Value, Assets Measured on Recurring Basis, Observable and Unobservable Input Reconciliation [Line Items]    
Warrants term 4 years 10 days 4 years 3 months 10 days
Expected Life (Years) | July 2024 Private Placement Warrants    
Fair Value, Assets Measured on Recurring Basis, Observable and Unobservable Input Reconciliation [Line Items]    
Warrants term 3 years 3 months 3 years 6 months
Expected Life (Years) | November 2025 Private Placement Warrants    
Fair Value, Assets Measured on Recurring Basis, Observable and Unobservable Input Reconciliation [Line Items]    
Warrants term 4 years 8 months 15 days 4 years 11 months 1 day
Expected Life (Years) | Inducement Warrants    
Fair Value, Assets Measured on Recurring Basis, Observable and Unobservable Input Reconciliation [Line Items]    
Warrants term 5 years 3 months  
Expected Life (Years) | Public Offering Warrants    
Fair Value, Assets Measured on Recurring Basis, Observable and Unobservable Input Reconciliation [Line Items]    
Warrants term 3 years 3 months 3 years 6 months
Expected Life (Years) | Legacy Allurion Other Common Stock    
Fair Value, Assets Measured on Recurring Basis, Observable and Unobservable Input Reconciliation [Line Items]    
Warrants term 1 year 4 months 24 days 1 year 8 months 8 days
Expected Life (Years) | Legacy Allurion Series C Preferred Stock Warrants    
Fair Value, Assets Measured on Recurring Basis, Observable and Unobservable Input Reconciliation [Line Items]    
Warrants term 5 years 5 years 3 months
Expected Life (Years) | Legacy Allurion Series D-1 Preferred Stock Warrants | Minimum    
Fair Value, Assets Measured on Recurring Basis, Observable and Unobservable Input Reconciliation [Line Items]    
Warrants term 5 years 5 years 3 months
Expected Life (Years) | Legacy Allurion Series D-1 Preferred Stock Warrants | Maximum    
Fair Value, Assets Measured on Recurring Basis, Observable and Unobservable Input Reconciliation [Line Items]    
Warrants term 6 years 6 months 6 years 8 months 15 days