v3.26.1
Financial Risk Management - VaR by Risk Category (Detail) - JPY (¥)
¥ in Billions
Mar. 31, 2026
Mar. 31, 2025
VaR for Trading Activity [Member] | Interest rate risk [Member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount ¥ 11.3 ¥ 18.3
VaR for Trading Activity [Member] | Interest rate risk [Member] | Maximum [member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 13.5 24.1
VaR for Trading Activity [Member] | Interest rate risk [Member] | Minimum [member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 6.5 17.8
VaR for Trading Activity [Member] | Interest rate risk [Member] | Daily average [Member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 10.8 19.5
VaR for Trading Activity [Member] | Currency risk [Member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 8.2 7.1
VaR for Trading Activity [Member] | Currency risk [Member] | Maximum [member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 9.5 8.4
VaR for Trading Activity [Member] | Currency risk [Member] | Minimum [member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 5.2 4.5
VaR for Trading Activity [Member] | Currency risk [Member] | Daily average [Member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 7.5 6.5
VaR for Trading Activity [Member] | Equities and commodities risk [Member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 1.3 3.0
VaR for Trading Activity [Member] | Equities and commodities risk [Member] | Maximum [member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 6.1 22.3
VaR for Trading Activity [Member] | Equities and commodities risk [Member] | Minimum [member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 1.1 2.9
VaR for Trading Activity [Member] | Equities and commodities risk [Member] | Daily average [Member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 1.9 5.7
VaR for Trading Activity [Member] | Other risk [Member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 1.4 19.1
VaR for Trading Activity [Member] | Other risk [Member] | Maximum [member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 2.4 21.5
VaR for Trading Activity [Member] | Other risk [Member] | Minimum [member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 0.8 12.4
VaR for Trading Activity [Member] | Other risk [Member] | Daily average [Member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 1.4 17.0
VaR for Trading Activity [Member] | Market risk [member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 7.9 40.8
VaR for Trading Activity [Member] | Market risk [member] | Maximum [member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 12.2 61.8
VaR for Trading Activity [Member] | Market risk [member] | Minimum [member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 7.6 38.4
VaR for Trading Activity [Member] | Market risk [member] | Daily average [Member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 9.0 42.1
VaR for Trading Activity [Member] | Sumitomo mitsui banking corporation [member] | Interest rate risk [Member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 10.0 5.7
VaR for Trading Activity [Member] | Sumitomo mitsui banking corporation [member] | Interest rate risk [Member] | Maximum [member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 12.3 7.2
VaR for Trading Activity [Member] | Sumitomo mitsui banking corporation [member] | Interest rate risk [Member] | Minimum [member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 5.4 4.4
VaR for Trading Activity [Member] | Sumitomo mitsui banking corporation [member] | Interest rate risk [Member] | Daily average [Member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 9.5 6.0
VaR for Trading Activity [Member] | Sumitomo mitsui banking corporation [member] | Currency risk [Member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 7.3 5.4
VaR for Trading Activity [Member] | Sumitomo mitsui banking corporation [member] | Currency risk [Member] | Maximum [member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 8.5 6.7
VaR for Trading Activity [Member] | Sumitomo mitsui banking corporation [member] | Currency risk [Member] | Minimum [member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 4.2 3.2
VaR for Trading Activity [Member] | Sumitomo mitsui banking corporation [member] | Currency risk [Member] | Daily average [Member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 6.5 5.1
VaR for Trading Activity [Member] | Sumitomo mitsui banking corporation [member] | Equities and commodities risk [Member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 0.3 0.2
VaR for Trading Activity [Member] | Sumitomo mitsui banking corporation [member] | Equities and commodities risk [Member] | Maximum [member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 2.5 2.4
VaR for Trading Activity [Member] | Sumitomo mitsui banking corporation [member] | Equities and commodities risk [Member] | Minimum [member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 0.2 0.1
VaR for Trading Activity [Member] | Sumitomo mitsui banking corporation [member] | Equities and commodities risk [Member] | Daily average [Member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 0.6 0.7
VaR for Trading Activity [Member] | Sumitomo mitsui banking corporation [member] | Other risk [Member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 1.4 19.1
VaR for Trading Activity [Member] | Sumitomo mitsui banking corporation [member] | Other risk [Member] | Maximum [member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 2.4 21.5
VaR for Trading Activity [Member] | Sumitomo mitsui banking corporation [member] | Other risk [Member] | Minimum [member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 0.8 12.4
VaR for Trading Activity [Member] | Sumitomo mitsui banking corporation [member] | Other risk [Member] | Daily average [Member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 1.4 17.0
VaR for Trading Activity [Member] | Sumitomo mitsui banking corporation [member] | Market risk [member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 4.7 23.9
VaR for Trading Activity [Member] | Sumitomo mitsui banking corporation [member] | Market risk [member] | Maximum [member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 7.7 26.9
VaR for Trading Activity [Member] | Sumitomo mitsui banking corporation [member] | Market risk [member] | Minimum [member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 4.3 17.8
VaR for Trading Activity [Member] | Sumitomo mitsui banking corporation [member] | Market risk [member] | Daily average [Member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 5.7 22.6
VaR for Non-trading Activity - Banking [Member] | Interest rate risk [Member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 82.9 62.5
VaR for Non-trading Activity - Banking [Member] | Interest rate risk [Member] | Maximum [member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 106.1 82.1
VaR for Non-trading Activity - Banking [Member] | Interest rate risk [Member] | Minimum [member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 62.7 57.6
VaR for Non-trading Activity - Banking [Member] | Interest rate risk [Member] | Daily average [Member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 88.4 68.2
VaR for Non-trading Activity - Banking [Member] | Currency risk [Member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 0.1 0.1
VaR for Non-trading Activity - Banking [Member] | Currency risk [Member] | Maximum [member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 4.1 0.2
VaR for Non-trading Activity - Banking [Member] | Currency risk [Member] | Minimum [member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 0.0 0.0
VaR for Non-trading Activity - Banking [Member] | Currency risk [Member] | Daily average [Member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 0.2 0.0
VaR for Non-trading Activity - Banking [Member] | Equities and commodities risk [Member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 24.3 32.6
VaR for Non-trading Activity - Banking [Member] | Equities and commodities risk [Member] | Maximum [member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 34.6 35.6
VaR for Non-trading Activity - Banking [Member] | Equities and commodities risk [Member] | Minimum [member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 19.0 12.6
VaR for Non-trading Activity - Banking [Member] | Equities and commodities risk [Member] | Daily average [Member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 25.8 28.0
VaR for Non-trading Activity - Banking [Member] | Other risk [Member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 0.0 0.0
VaR for Non-trading Activity - Banking [Member] | Other risk [Member] | Maximum [member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 0.0 0.0
VaR for Non-trading Activity - Banking [Member] | Other risk [Member] | Minimum [member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 0.0 0.0
VaR for Non-trading Activity - Banking [Member] | Other risk [Member] | Daily average [Member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 0.0 0.0
VaR for Non-trading Activity - Banking [Member] | Market risk [member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 89.3 63.6
VaR for Non-trading Activity - Banking [Member] | Market risk [member] | Maximum [member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 126.1 96.3
VaR for Non-trading Activity - Banking [Member] | Market risk [member] | Minimum [member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 60.2 59.5
VaR for Non-trading Activity - Banking [Member] | Market risk [member] | Daily average [Member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 94.3 75.0
VaR for Non-trading Activity - Banking [Member] | Sumitomo mitsui banking corporation [member] | Interest rate risk [Member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 81.3 61.3
VaR for Non-trading Activity - Banking [Member] | Sumitomo mitsui banking corporation [member] | Interest rate risk [Member] | Maximum [member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 104.7 80.6
VaR for Non-trading Activity - Banking [Member] | Sumitomo mitsui banking corporation [member] | Interest rate risk [Member] | Minimum [member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 61.6 56.4
VaR for Non-trading Activity - Banking [Member] | Sumitomo mitsui banking corporation [member] | Interest rate risk [Member] | Daily average [Member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 87.1 66.9
VaR for Non-trading Activity - Banking [Member] | Sumitomo mitsui banking corporation [member] | Currency risk [Member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 0.1 0.1
VaR for Non-trading Activity - Banking [Member] | Sumitomo mitsui banking corporation [member] | Currency risk [Member] | Maximum [member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 4.1 0.2
VaR for Non-trading Activity - Banking [Member] | Sumitomo mitsui banking corporation [member] | Currency risk [Member] | Minimum [member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 0.0 0.0
VaR for Non-trading Activity - Banking [Member] | Sumitomo mitsui banking corporation [member] | Currency risk [Member] | Daily average [Member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 0.2 0.0
VaR for Non-trading Activity - Banking [Member] | Sumitomo mitsui banking corporation [member] | Equities and commodities risk [Member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 24.3 32.6
VaR for Non-trading Activity - Banking [Member] | Sumitomo mitsui banking corporation [member] | Equities and commodities risk [Member] | Maximum [member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 34.6 35.6
VaR for Non-trading Activity - Banking [Member] | Sumitomo mitsui banking corporation [member] | Equities and commodities risk [Member] | Minimum [member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 19.0 12.6
VaR for Non-trading Activity - Banking [Member] | Sumitomo mitsui banking corporation [member] | Equities and commodities risk [Member] | Daily average [Member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 25.8 28.0
VaR for Non-trading Activity - Banking [Member] | Sumitomo mitsui banking corporation [member] | Other risk [Member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 0.0 0.0
VaR for Non-trading Activity - Banking [Member] | Sumitomo mitsui banking corporation [member] | Other risk [Member] | Maximum [member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 0.0 0.0
VaR for Non-trading Activity - Banking [Member] | Sumitomo mitsui banking corporation [member] | Other risk [Member] | Minimum [member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 0.0 0.0
VaR for Non-trading Activity - Banking [Member] | Sumitomo mitsui banking corporation [member] | Other risk [Member] | Daily average [Member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 0.0 0.0
VaR for Non-trading Activity - Banking [Member] | Sumitomo mitsui banking corporation [member] | Market risk [member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 87.7 62.5
VaR for Non-trading Activity - Banking [Member] | Sumitomo mitsui banking corporation [member] | Market risk [member] | Maximum [member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 124.6 94.7
VaR for Non-trading Activity - Banking [Member] | Sumitomo mitsui banking corporation [member] | Market risk [member] | Minimum [member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 59.1 58.2
VaR for Non-trading Activity - Banking [Member] | Sumitomo mitsui banking corporation [member] | Market risk [member] | Daily average [Member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 93.0 73.7
VaR for Non-trading Activity - Strategic Equity Investment [Member] | Equity risk [Member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 1,337.5 1,323.4
VaR for Non-trading Activity - Strategic Equity Investment [Member] | Equity risk [Member] | Maximum [member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 1,621.0 1,576.8
VaR for Non-trading Activity - Strategic Equity Investment [Member] | Equity risk [Member] | Minimum [member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 1,147.9 1,233.7
VaR for Non-trading Activity - Strategic Equity Investment [Member] | Equity risk [Member] | Daily average [Member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 1,455.4 1,456.7
VaR for Non-trading Activity - Strategic Equity Investment [Member] | Sumitomo mitsui banking corporation [member] | Equity risk [Member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 1,012.6 960.3
VaR for Non-trading Activity - Strategic Equity Investment [Member] | Sumitomo mitsui banking corporation [member] | Equity risk [Member] | Maximum [member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 1,272.5 1,258.2
VaR for Non-trading Activity - Strategic Equity Investment [Member] | Sumitomo mitsui banking corporation [member] | Equity risk [Member] | Minimum [member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount 832.8 937.3
VaR for Non-trading Activity - Strategic Equity Investment [Member] | Sumitomo mitsui banking corporation [member] | Equity risk [Member] | Daily average [Member]    
Disclosure of nature and extent of risks arising from financial instruments [line items]    
Value at risk amount ¥ 1,105.8 ¥ 1,134.5