v3.26.1
Other Expenses - Summary of Other Expenses (Parenthetical) (Detail) - JPY (¥)
¥ in Millions
12 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Mar. 31, 2024
SMBC Rail Services LLC [Member]      
Disclosure of associates [line items]      
Adjustments for gain (loss) on disposal of investments in subsidiaries, joint ventures and associates     ¥ (84,578)
The Bank of East Asia, Limited [member]      
Disclosure of associates [line items]      
Adjustments for gain (loss) on disposal of investments in subsidiaries, joint ventures and associates ¥ (48,194)    
Impairment Loss Recognized In Profit Or Loss Investments In Associates And Joint Ventures     18,935
VPBank SMBC Finance Company Limited [member]      
Disclosure of associates [line items]      
Impairment Loss Recognized In Profit Or Loss Investments In Associates And Joint Ventures   ¥ 59,264 ¥ 64,709
Vietnam Prosperity Joint Stock Commercial Bank [Member]      
Disclosure of associates [line items]      
Impairment Loss Recognized In Profit Or Loss Investments In Associates And Joint Ventures   ¥ 74,982