Fair Value of Financial Assets and Liabilities - Impact of Valuation Sensitivity (Detail) - JPY (¥) ¥ in Millions	12 Months Ended
Mar. 31, 2023	Mar. 31, 2022	Mar. 31, 2021
Financial assets:
Financial assets at fair value through profit or loss	¥ 1,488,239	¥ 1,695,585
Financial liabilities:
Financial liabilities designated at fair value through profit or loss	(414,106)	(455,734)
Others	8,522,212	7,809,677
At fair value [member]
Financial assets:
Financial assets at fair value through profit or loss	1,488,239	1,695,585
Investment securities at fair value through other comprehensive income	27,360,031	32,665,451
Financial liabilities:
Financial liabilities designated at fair value through profit or loss	(414,106)	(455,734)
At fair value [member] \| Level 3 [member]
Financial assets:
Derivative financial instruments	1,029,481	919,971	¥ 873,801
Financial assets at fair value through profit or loss	735,668	728,897
Investment securities at fair value through other comprehensive income	464,821	468,713
Financial liabilities:
Financial liabilities designated at fair value through profit or loss	(185,020)	(291,086)
At fair value [member] \| Level 3 [member] \| Financial liabilities at fair value through profit or loss, category [member]
Financial assets:
Derivative financial instruments	(185,020)	(291,086)	(166,896)
Financial liabilities:
Financial liabilities designated at fair value through profit or loss	(185,020)	(291,086)
At fair value [member] \| Level 3 [member] \| Financial liabilities at fair value through profit or loss, category [member] \| Recorded in profit and loss [member]
Financial liabilities:
Financial liabilities, Favorable changes	1,007	2,008
Financial liabilities, Unfavorable changes	1,109	2,319
At fair value [member] \| Level 3 [member] \| Debt instruments [member]
Financial assets:
Financial assets at fair value through profit or loss	650,467	693,013
At fair value [member] \| Level 3 [member] \| Others [member]
Financial liabilities:
Others	7,852	3,052
At fair value [member] \| Level 3 [member] \| Others [member] \| Recorded in profit and loss [member]
Financial liabilities:
Financial liabilities, Favorable changes	62	126
Financial liabilities, Unfavorable changes	61	118
At fair value [member] \| Level 3 [member] \| Derivative financial assets [member] \| Interest rate derivatives [member]
Financial assets:
Derivative financial instruments	(3,248)	(7,162)
At fair value [member] \| Level 3 [member] \| Derivative financial assets [member] \| Currency derivatives [member]
Financial assets:
Derivative financial instruments	(4,567)	1,652
At fair value [member] \| Level 3 [member] \| Derivative financial assets [member] \| Currency derivatives [member] \| Recorded in profit and loss [member]
Financial assets:
Financial assets, Favorable changes	6	75
Financial assets, Unfavorable changes	6	73
At fair value [member] \| Level 3 [member] \| Derivative financial assets [member] \| Equity derivatives [member]
Financial assets:
Derivative financial instruments	13,825	15,384
At fair value [member] \| Level 3 [member] \| Derivative financial assets [member] \| Equity derivatives [member] \| Recorded in profit and loss [member]
Financial assets:
Financial assets, Favorable changes	2,462	3,274
Financial assets, Unfavorable changes	2,467	3,309
At fair value [member] \| Level 3 [member] \| Derivative financial assets [member] \| Credit derivatives [member]
Financial assets:
Derivative financial instruments	150	521
At fair value [member] \| Level 3 [member] \| Derivative financial assets [member] \| Credit derivatives [member] \| Recorded in profit and loss [member]
Financial assets:
Financial assets, Favorable changes	17	17
Financial assets, Unfavorable changes	17	18
At fair value [member] \| Level 3 [member] \| Financial assets at fair value through profit or loss [member]
Financial assets:
Derivative financial instruments	735,668	728,897	594,227
At fair value [member] \| Level 3 [member] \| Financial assets at fair value through profit or loss [member] \| Debt instruments [member]
Financial assets:
Derivative financial instruments	650,467	693,013	561,450
At fair value [member] \| Level 3 [member] \| Financial assets at fair value through profit or loss [member] \| Debt instruments [member] \| Recorded in profit and loss [member]
Financial assets:
Financial assets, Favorable changes	917	3,347
Financial assets, Unfavorable changes	4,533	7,422
At fair value [member] \| Level 3 [member] \| Financial assets at fair value through profit or loss [member] \| Equity instruments [member]
Financial assets:
Derivative financial instruments	85,201	35,884	32,777
At fair value [member] \| Level 3 [member] \| Financial assets at fair value through profit or loss [member] \| Equity instruments [member] \| Recorded in profit and loss [member]
Financial assets:
Financial assets, Favorable changes	362	88
Financial assets, Unfavorable changes	875	167
At fair value [member] \| Level 3 [member] \| Financial assets at fair value through other comprehensive income, category [member]
Financial assets:
Derivative financial instruments	464,821	468,713	447,605
At fair value [member] \| Level 3 [member] \| Financial assets at fair value through other comprehensive income, category [member] \| Equity instruments [member]
Financial assets:
Derivative financial instruments	464,821	468,713	¥ 447,605
Financial assets at fair value through profit or loss	85,201	35,884
Investment securities at fair value through other comprehensive income	464,821	468,713
At fair value [member] \| Level 3 [member] \| Financial assets at fair value through other comprehensive income, category [member] \| Equity instruments [member] \| Recorded in equity [member]
Financial assets:
Financial assets, Favorable changes	15,368	12,914
Financial assets, Unfavorable changes	¥ 15,368	¥ 12,019

The amount of decrease in the fair value measurement of assets due to a change in multiple unobservable inputs to reflect reasonably possible alternative assumptions.

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The amount of decrease in the fair value measurement of liabilities due to a change in multiple unobservable inputs to reflect reasonably possible alternative assumptions.

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The amount of financial assets at fair value through other comprehensive income. [Refer: At fair value [member]; Financial assets; Other comprehensive income]

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The amount of financial assets mandatorily measured at fair value through profit or loss in accordance with IFRS 9. [Refer: Financial assets at fair value through profit or loss]

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The amount of financial liabilities that meet either of the following conditions: (a) they meet the definition of held for trading; or (b) upon initial recognition they are designated by the entity as at fair value through profit or loss. An entity may use this designation only when permitted by paragraph 4.3.5 of IFRS 9 (embedded derivatives) or when doing so results in more relevant information, because either: (a) it eliminates or significantly reduces a measurement or recognition inconsistency (sometimes referred to as ‘an accounting mismatch’) that would otherwise arise from measuring assets or liabilities or recognising the gains and losses on them on different bases; or (b) a group of financial liabilities or financial assets and financial liabilities is managed and its performance is evaluated on a fair value basis, in accordance with a documented risk management or investment strategy, and information about the group is provided internally on that basis to the entity’s key management personnel (as defined in IAS 24). [Refer: At fair value [member]; Key management personnel of entity or parent [member]; Derivatives [member]; Financial assets; Financial liabilities]

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The amount of increase in the fair value measurement of assets due to a change in multiple unobservable inputs to reflect reasonably possible alternative assumptions.

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The amount of financial liabilities that the entity does not separately disclose in the same statement or note. [Refer: Financial liabilities]

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