v3.25.2
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, 2025
Mar. 31, 2024
Disclosure of fair value measurement of financial assets and liabilities [Line items]    
Financial assets measured at fair value through profit or loss ¥ 1,379,534 ¥ 1,540,232
Financial assets measured at fair value through other comprehensive income 12,336,269 12,121,213
Financial liabilities measured at fair value through profit or loss (319,881) (432,189)
Derivative financial instruments [Member]    
Disclosure of fair value measurement of financial assets and liabilities [Line items]    
Financial liabilities measured at fair value through profit or loss (319,881) (432,189)
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 231,713 221,743
Financial assets measured at fair value through other comprehensive income 9,078,437 8,279,783
Stocks [Member]    
Disclosure of fair value measurement of financial assets and liabilities [Line items]    
Financial assets measured at fair value through profit or loss 46,215 212,393
Financial assets measured at fair value through other comprehensive income 3,246,885 3,829,893
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 618,228 553,174
Derivative financial instruments [Member]    
Disclosure of fair value measurement of financial assets and liabilities [Line items]    
Financial assets measured at fair value through profit or loss 483,378 552,921
Others [Member]    
Disclosure of fair value measurement of financial assets and liabilities [Line items]    
Financial assets measured at fair value through other comprehensive income 10,947 11,537
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 397,315 393,438
Financial assets measured at fair value through other comprehensive income 7,552,875 7,897,972
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 110,516 105,367
Financial assets measured at fair value through other comprehensive income 4,487,174 4,245,238
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 3,054,754 3,641,197
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 286,799 288,071
Level 1 [Member] | Others [Member]    
Disclosure of fair value measurement of financial assets and liabilities [Line items]    
Financial assets measured at fair value through other comprehensive income 10,947 11,537
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 900,495 924,193
Financial assets measured at fair value through other comprehensive income 4,571,862 4,013,583
Financial liabilities measured at fair value through profit or loss (319,881) (432,189)
Level 2 [Member] | Derivative financial instruments [Member]    
Disclosure of fair value measurement of financial assets and liabilities [Line items]    
Financial liabilities measured at fair value through profit or loss (319,881) (432,189)
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 110,488 106,169
Financial assets measured at fair value through other comprehensive income 4,571,862 4,013,583
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 331,429 265,103
Level 2 [Member] | Derivative financial instruments [Member]    
Disclosure of fair value measurement of financial assets and liabilities [Line items]    
Financial assets measured at fair value through profit or loss 458,579 552,921
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 81,724 222,601
Financial assets measured at fair value through other comprehensive income 211,532 209,658
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 10,710 10,208
Financial assets measured at fair value through other comprehensive income 19,401 20,962
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 46,215 212,393
Financial assets measured at fair value through other comprehensive income 192,131 ¥ 188,696
Level 3 [Member] | Derivative financial instruments [Member]    
Disclosure of fair value measurement of financial assets and liabilities [Line items]    
Financial assets measured at fair value through profit or loss ¥ 24,800