Fair Value Measurements - Schedule of Assumptions used in Pricing Model (Details) - Black-Scholes Option Pricing Model - Level 3	Mar. 31, 2024	Dec. 31, 2023
Interest Rate | Other Common Stock
Fair Value, Assets Measured on Recurring Basis, Observable and Unobservable Input Reconciliation [Line Items]
Warrants measurement input	0.0436	0.0395
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	0.042	0.0388
Interest Rate | 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	0.042	0.0388
Exercise Price | Other Common Stock
Fair Value, Assets Measured on Recurring Basis, Observable and Unobservable Input Reconciliation [Line Items]
Warrants measurement input	1.05	1.05
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	6.73	6.73
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	12.14	12.14
Estimated Fair Value of Underlying Share Price | Other Common Stock
Fair Value, Assets Measured on Recurring Basis, Observable and Unobservable Input Reconciliation [Line Items]
Warrants measurement input	1.75	3.74
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	1.75	3.74
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	1.75	3.74
Expected Volatility | Other Common Stock
Fair Value, Assets Measured on Recurring Basis, Observable and Unobservable Input Reconciliation [Line Items]
Warrants measurement input	0.90	1
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	0.90	1
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	0.90	1
Expected Life (Years) | Other Common Stock
Fair Value, Assets Measured on Recurring Basis, Observable and Unobservable Input Reconciliation [Line Items]
Warrants term	3 years 5 months 8 days	3 years 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	7 years	7 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	7 years	7 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	8 years 5 months 15 days	8 years 8 months 15 days