v3.26.1
Income Taxes - Summary of Components of Deferred Tax Assets and Liabilities (Detail) - JPY (¥)
¥ in Millions
Mar. 31, 2026
Mar. 31, 2025
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]    
Deferred tax assets ¥ 555,596 ¥ 517,869
Deferred tax liabilities (1,584,505) (1,659,433)
Net deferred tax assets and liabilities (1,028,909) (1,141,564)
Deferred tax assets [Member]    
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]    
Deferred tax assets 2,906,926 2,129,712
Deferred tax assets [Member] | Defined Benefit Plan [Member]    
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]    
Deferred tax assets 177,494 156,650
Deferred tax assets [Member] | Accrued expenses and liabilities for quality assurance [Member]    
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]    
Deferred tax assets 886,672 821,680
Deferred tax assets [Member] | Other accrued employees' compensation [Member]    
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]    
Deferred tax assets 160,993 146,548
Deferred tax assets [Member] | Operating loss carryforwards for tax purposes [Member]    
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]    
Deferred tax assets 357,926 44,324
Deferred tax assets [Member] | Allowance for doubtful accounts and credit losses [Member]    
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]    
Deferred tax assets 130,858 115,209
Deferred tax assets [Member] | Property plant equipment and other assets [Member]    
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]    
Deferred tax assets 339,623 340,410
Deferred tax assets [Member] | Other [Member]    
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]    
Deferred tax assets 853,359 504,892
Deferred tax liabilities [Member]    
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]    
Deferred tax liabilities (3,935,835) (3,271,276)
Deferred tax liabilities [Member] | Changes in fair value of financial instruments measured in other comprehensive income [Member]    
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]    
Deferred tax liabilities (751,808) (727,581)
Deferred tax liabilities [Member] | Undistributed earnings of foreign subsidiaries [Member]    
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]    
Deferred tax liabilities (48,979) (63,179)
Deferred tax liabilities [Member] | Undistributed earnings of associates and joint ventures [Member]    
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]    
Deferred tax liabilities (1,289,418) (1,223,489)
Deferred tax liabilities [Member] | Basis difference of acquired assets [Member]    
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]    
Deferred tax liabilities (90,855) (71,386)
Deferred tax liabilities [Member] | Capitalised development costs [Member]    
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]    
Deferred tax liabilities (171,315) (181,775)
Deferred tax liabilities [Member] | Lease transactions [Member]    
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]    
Deferred tax liabilities (1,337,570) (860,487)
Deferred tax liabilities [Member] | Other [Member]    
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]    
Deferred tax liabilities ¥ (245,890) ¥ (143,379)