v3.25.2
Retirement benefits - Plan Investment Assets for Gratuity Funds and Pension Fund Measured at Fair Value by Level and in Total (Detail)
₨ in Millions, $ in Millions
Mar. 31, 2025
INR (₨)
Mar. 31, 2025
USD ($)
Mar. 31, 2024
INR (₨)
Fair Value Measurements Using Quoted Prices In Active Markets for Identical Assets (Level 1)      
Defined Benefit Plan Disclosure [Line Items]      
Plan investment assets at fair value ₨ 649.8 $ 7.6 ₨ 581.9
Fair Value Measurements Using Quoted Prices In Active Markets for Identical Assets (Level 1) | Funds managed by insurance company (1)      
Defined Benefit Plan Disclosure [Line Items]      
Plan investment assets at fair value 0.0   0.0
Fair Value Measurements Using Quoted Prices In Active Markets for Identical Assets (Level 1) | Funds managed by insurance company (2)      
Defined Benefit Plan Disclosure [Line Items]      
Plan investment assets at fair value 0.0   0.0
Fair Value Measurements Using Quoted Prices In Active Markets for Identical Assets (Level 1) | Government Securities Managed by Trust      
Defined Benefit Plan Disclosure [Line Items]      
Plan investment assets at fair value 0.0   0.0
Fair Value Measurements Using Quoted Prices In Active Markets for Identical Assets (Level 1) | Debenture and Bonds Managed by Trust      
Defined Benefit Plan Disclosure [Line Items]      
Plan investment assets at fair value 0.0   0.0
Fair Value Measurements Using Quoted Prices In Active Markets for Identical Assets (Level 1) | Other Funds Managed by Trust      
Defined Benefit Plan Disclosure [Line Items]      
Plan investment assets at fair value 649.8   581.9
Fair Value Measurements Using Significant other observable inputs (Level 2)      
Defined Benefit Plan Disclosure [Line Items]      
Plan investment assets at fair value 18,972.6 222.0 17,672.3
Fair Value Measurements Using Significant other observable inputs (Level 2) | Funds managed by insurance company (1)      
Defined Benefit Plan Disclosure [Line Items]      
Plan investment assets at fair value 0.0   0.0
Fair Value Measurements Using Significant other observable inputs (Level 2) | Funds managed by insurance company (2)      
Defined Benefit Plan Disclosure [Line Items]      
Plan investment assets at fair value 15,803.1   14,478.3
Fair Value Measurements Using Significant other observable inputs (Level 2) | Government Securities Managed by Trust      
Defined Benefit Plan Disclosure [Line Items]      
Plan investment assets at fair value 1,799.5   1,792.6
Fair Value Measurements Using Significant other observable inputs (Level 2) | Debenture and Bonds Managed by Trust      
Defined Benefit Plan Disclosure [Line Items]      
Plan investment assets at fair value 1,131.1   1,200.9
Fair Value Measurements Using Significant other observable inputs (Level 2) | Other Funds Managed by Trust      
Defined Benefit Plan Disclosure [Line Items]      
Plan investment assets at fair value 238.9   200.5
Fair Value Measurements Using Significant unobservable inputs (Level 3)      
Defined Benefit Plan Disclosure [Line Items]      
Plan investment assets at fair value 769.1 $ 9.0 859.1
Fair Value Measurements Using Significant unobservable inputs (Level 3) | Funds managed by insurance company (1)      
Defined Benefit Plan Disclosure [Line Items]      
Plan investment assets at fair value 769.1   859.1
Fair Value Measurements Using Significant unobservable inputs (Level 3) | Funds managed by insurance company (2)      
Defined Benefit Plan Disclosure [Line Items]      
Plan investment assets at fair value 0.0   0.0
Fair Value Measurements Using Significant unobservable inputs (Level 3) | Government Securities Managed by Trust      
Defined Benefit Plan Disclosure [Line Items]      
Plan investment assets at fair value 0.0   0.0
Fair Value Measurements Using Significant unobservable inputs (Level 3) | Debenture and Bonds Managed by Trust      
Defined Benefit Plan Disclosure [Line Items]      
Plan investment assets at fair value 0.0   0.0
Fair Value Measurements Using Significant unobservable inputs (Level 3) | Other Funds Managed by Trust      
Defined Benefit Plan Disclosure [Line Items]      
Plan investment assets at fair value ₨ 0.0   ₨ 0.0