v3.26.1
Fair Value Measurements - Fair Values of Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - Fair value, measurements, recurring [Member] - JPY (¥)
¥ in Millions
Mar. 31, 2026
Mar. 31, 2025
Disclosure of fair value measurement of financial assets and liabilities [Line items]    
Financial assets measured at fair value through profit or loss ¥ 2,279,925 ¥ 1,379,534
Financial assets measured at fair value through other comprehensive income 11,137,940 12,336,269
Financial liabilities measured at fair value through profit or loss (357,955) (319,881)
Public and corporate bonds [Member]    
Disclosure of fair value measurement of financial assets and liabilities [Line items]    
Financial assets measured at fair value through profit or loss 267,623 231,713
Financial assets measured at fair value through other comprehensive income 7,552,906 9,078,437
Stocks [Member]    
Disclosure of fair value measurement of financial assets and liabilities [Line items]    
Financial assets measured at fair value through profit or loss 884,667 46,215
Financial assets measured at fair value through other comprehensive income 3,575,178 3,246,885
Investment trusts [Member]    
Disclosure of fair value measurement of financial assets and liabilities [Line items]    
Financial assets measured at fair value through profit or loss 648,189 618,228
Interest rate and currency swap [member]    
Disclosure of fair value measurement of financial assets and liabilities [Line items]    
Financial assets measured at fair value through profit or loss 414,706 395,588
Financial liabilities measured at fair value through profit or loss (300,486) (303,670)
Foreign exchange forward, option and other contracts [Member]    
Disclosure of fair value measurement of financial assets and liabilities [Line items]    
Financial assets measured at fair value through profit or loss 64,741 87,790
Financial liabilities measured at fair value through profit or loss (57,469) (16,211)
Other [Member]    
Disclosure of fair value measurement of financial assets and liabilities [Line items]    
Financial assets measured at fair value through other comprehensive income 9,855 10,947
Level 1 [Member]    
Disclosure of fair value measurement of financial assets and liabilities [Line items]    
Financial assets measured at fair value through profit or loss 475,796 397,315
Financial assets measured at fair value through other comprehensive income 7,770,835 7,552,875
Level 1 [Member] | Public and corporate bonds [Member]    
Disclosure of fair value measurement of financial assets and liabilities [Line items]    
Financial assets measured at fair value through profit or loss 123,344 110,516
Financial assets measured at fair value through other comprehensive income 4,449,366 4,487,174
Level 1 [Member] | Stocks [Member]    
Disclosure of fair value measurement of financial assets and liabilities [Line items]    
Financial assets measured at fair value through other comprehensive income 3,311,613 3,054,754
Level 1 [Member] | Investment trusts [Member]    
Disclosure of fair value measurement of financial assets and liabilities [Line items]    
Financial assets measured at fair value through profit or loss 352,452 286,799
Level 1 [Member] | Other [Member]    
Disclosure of fair value measurement of financial assets and liabilities [Line items]    
Financial assets measured at fair value through other comprehensive income 9,855 10,947
Level 2 [Member]    
Disclosure of fair value measurement of financial assets and liabilities [Line items]    
Financial assets measured at fair value through profit or loss 855,468 900,495
Financial assets measured at fair value through other comprehensive income 3,084,093 4,571,862
Financial liabilities measured at fair value through profit or loss (357,955) (319,881)
Level 2 [Member] | Public and corporate bonds [Member]    
Disclosure of fair value measurement of financial assets and liabilities [Line items]    
Financial assets measured at fair value through profit or loss 132,079 110,488
Financial assets measured at fair value through other comprehensive income 3,084,093 4,571,862
Level 2 [Member] | Investment trusts [Member]    
Disclosure of fair value measurement of financial assets and liabilities [Line items]    
Financial assets measured at fair value through profit or loss 295,737 331,429
Level 2 [Member] | Interest rate and currency swap [member]    
Disclosure of fair value measurement of financial assets and liabilities [Line items]    
Financial assets measured at fair value through profit or loss 414,706 395,588
Financial liabilities measured at fair value through profit or loss (300,486) (303,670)
Level 2 [Member] | Foreign exchange forward, option and other contracts [Member]    
Disclosure of fair value measurement of financial assets and liabilities [Line items]    
Financial assets measured at fair value through profit or loss 12,947 62,991
Financial liabilities measured at fair value through profit or loss (57,469) (16,211)
Level 3 [Member]    
Disclosure of fair value measurement of financial assets and liabilities [Line items]    
Financial assets measured at fair value through profit or loss 948,661 81,724
Financial assets measured at fair value through other comprehensive income 283,011 211,532
Level 3 [Member] | Public and corporate bonds [Member]    
Disclosure of fair value measurement of financial assets and liabilities [Line items]    
Financial assets measured at fair value through profit or loss 12,200 10,710
Financial assets measured at fair value through other comprehensive income 19,447 19,401
Level 3 [Member] | Stocks [Member]    
Disclosure of fair value measurement of financial assets and liabilities [Line items]    
Financial assets measured at fair value through profit or loss 884,667 46,215
Financial assets measured at fair value through other comprehensive income 263,565 192,131
Level 3 [Member] | Foreign exchange forward, option and other contracts [Member]    
Disclosure of fair value measurement of financial assets and liabilities [Line items]    
Financial assets measured at fair value through profit or loss ¥ 51,795 ¥ 24,800