v3.26.1
Retirement benefits - Plan Assets as Percentage of Total Funds (Detail) - Gratuity
Mar. 31, 2026
Funds managed by insurance company (1)  
Defined Benefit Plan Disclosure [Line Items]  
Plan asset as percentage of total funds 100.00% [1]
Funds managed by insurance company (1) | Government Securities  
Defined Benefit Plan Disclosure [Line Items]  
Plan asset as percentage of total funds 70.10% [1]
Funds managed by insurance company (1) | Debenture and bonds  
Defined Benefit Plan Disclosure [Line Items]  
Plan asset as percentage of total funds 6.80% [1]
Funds managed by insurance company (1) | Equity securities  
Defined Benefit Plan Disclosure [Line Items]  
Plan asset as percentage of total funds 10.60% [1]
Funds managed by insurance company (1) | Other  
Defined Benefit Plan Disclosure [Line Items]  
Plan asset as percentage of total funds 12.50% [1]
Funds managed by insurance company (2)  
Defined Benefit Plan Disclosure [Line Items]  
Plan asset as percentage of total funds 100.00% [1]
Funds managed by insurance company (2) | Government Securities  
Defined Benefit Plan Disclosure [Line Items]  
Plan asset as percentage of total funds 24.70% [1]
Funds managed by insurance company (2) | Debenture and bonds  
Defined Benefit Plan Disclosure [Line Items]  
Plan asset as percentage of total funds 31.70% [1]
Funds managed by insurance company (2) | Equity securities  
Defined Benefit Plan Disclosure [Line Items]  
Plan asset as percentage of total funds 38.20% [1]
Funds managed by insurance company (2) | Other  
Defined Benefit Plan Disclosure [Line Items]  
Plan asset as percentage of total funds 5.40% [1]
Funds managed by trust  
Defined Benefit Plan Disclosure [Line Items]  
Plan asset as percentage of total funds 100.00%
Funds managed by trust | Government Securities  
Defined Benefit Plan Disclosure [Line Items]  
Plan asset as percentage of total funds 34.60%
Funds managed by trust | Debenture and bonds  
Defined Benefit Plan Disclosure [Line Items]  
Plan asset as percentage of total funds 38.50%
Funds managed by trust | Equity securities  
Defined Benefit Plan Disclosure [Line Items]  
Plan asset as percentage of total funds 7.30%
Funds managed by trust | Other  
Defined Benefit Plan Disclosure [Line Items]  
Plan asset as percentage of total funds 19.60%
[1] The data pertaining to plan investment assets measured at fair value by level and in total as of March 31, 2026 are provided separately.