v3.26.1
Offsetting of Financial Assets and Liabilities - Summary of Offsetting of Financial Assets and Liabilities (Detail) - JPY (¥)
¥ in Millions
Mar. 31, 2026
Mar. 31, 2025
Disclosure of offsetting of financial assets and liabilities [Line Items]    
Financial assets, Gross amounts of recognized financial assets and liabilities ¥ 45,561,252 ¥ 35,284,514
Financial assets, Gross amounts offset in statement of financial position (9,999,410) (4,895,489)
Financial assets, Net amounts presented in statement of financial position 35,561,842 30,389,025
Financial assets, Related amounts not offset in statement of financial position, Financial instruments (31,367,727) (27,389,214)
Financial assets, Related amounts not offset in statement of financial position, Cash collateral (1,491,269) (800,137)
Financial assets, Net amounts 2,702,846 2,199,674
Financial liabilities, Gross amounts of recognized financial assets and liabilities 45,682,412 42,027,829
Financial liabilities, Gross amounts offset in statement of financial position (10,033,412) (4,933,470)
Financial liabilities, Net amounts presented in statement of financial position 35,649,000 37,094,359
Financial liabilities, Related amounts not offset in statement of financial position, Financial instruments (30,180,180) (33,127,437)
Financial liabilities, Related amounts not offset in statement of financial position, Cash collateral (1,127,588) (921,921)
Financial liabilities, Net amounts 4,341,232 3,045,001
Reverse repurchase agreements and cash collateral on securities borrowed [member]    
Disclosure of offsetting of financial assets and liabilities [Line Items]    
Financial assets, Gross amounts of recognized financial assets and liabilities 27,692,001 23,659,547
Financial assets, Gross amounts offset in statement of financial position (2,223,259) (1,583,538)
Financial assets, Net amounts presented in statement of financial position 25,468,742 22,076,009
Financial assets, Related amounts not offset in statement of financial position, Financial instruments (25,157,046) (21,842,958)
Financial assets, Net amounts 311,696 233,051
Derivative financial assets [member]    
Disclosure of offsetting of financial assets and liabilities [Line Items]    
Financial assets, Gross amounts of recognized financial assets and liabilities 17,869,251 11,624,967
Financial assets, Gross amounts offset in statement of financial position (7,776,151) (3,311,951)
Financial assets, Net amounts presented in statement of financial position 10,093,100 8,313,016
Financial assets, Related amounts not offset in statement of financial position, Financial instruments (6,210,681) (5,546,256)
Financial assets, Related amounts not offset in statement of financial position, Cash collateral (1,491,269) (800,137)
Financial assets, Net amounts 2,391,150 1,966,623
Repurchase agreements and cash collateral on securities lent [Member]    
Disclosure of offsetting of financial assets and liabilities [Line Items]    
Financial liabilities, Gross amounts of recognized financial assets and liabilities 26,399,815 29,374,639
Financial liabilities, Gross amounts offset in statement of financial position (2,223,259) (1,583,538)
Financial liabilities, Net amounts presented in statement of financial position 24,176,556 27,791,101
Financial liabilities, Related amounts not offset in statement of financial position, Financial instruments (24,081,418) (27,603,758)
Financial liabilities, Net amounts 95,138 187,343
Derivative financial liabilities [member]    
Disclosure of offsetting of financial assets and liabilities [Line Items]    
Financial liabilities, Gross amounts of recognized financial assets and liabilities 19,282,597 12,653,190
Financial liabilities, Gross amounts offset in statement of financial position (7,810,153) (3,349,932)
Financial liabilities, Net amounts presented in statement of financial position 11,472,444 9,303,258
Financial liabilities, Related amounts not offset in statement of financial position, Financial instruments (6,098,762) (5,523,679)
Financial liabilities, Related amounts not offset in statement of financial position, Cash collateral (1,127,588) (921,921)
Financial liabilities, Net amounts ¥ 4,246,094 ¥ 2,857,658