Other Assets and Liabilities (Details of Other Assets and Liabilities) (Parenthetical) (Detail) - JPY (¥) ¥ in Millions		Mar. 31, 2020	Mar. 31, 2019
Other Assets and Other Liabilities [Line Items]
Accounts receivable from brokers, dealers and customers for securities transactions	[1]	¥ 783,439	¥ 1,517,235
Accounts payable to brokers, dealers and customers for securities transactions	[1]	2,161,075	2,572,315
Consolidated VIEs
Other Assets and Other Liabilities [Line Items]
Accounts receivable from brokers, dealers and customers for securities transactions		3,136	555,938
Accounts payable to brokers, dealers and customers for securities transactions		¥ 3,225	¥ 620,766

[1] Receivables from brokers, dealers and customers for securities transactions included ¥555,938 million and ¥3,136 million of such receivables of consolidated VIEs at March 31, 2019 and 2020, respectively. Payables to brokers, dealers and customers for securities transactions included ¥620,766 million and ¥3,225 million of such payables of consolidated VIEs at March 31, 2019 and 2020, respectively.