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Regulatory Matters - Additional Information (Detail) $ in Billions | Jun. 30, 2021 USD ($) | Mar. 31, 2020
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Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items] |  |
Maximum Asset Value Required To Be Maintained Leverage Ratio | $ 10 |
Tier 1 capital ratio of risk-weighted assets | 0.025 |
Covid 19[Member] | Throughout Two Thousand And Twenty [Member] |  |
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items] |  |
Leverage ratio | 0.08 |
Tier One Leverage Capital to Average Assets | 0.08 |
Covid 19[Member] | Throughout Two Thousand And Twenty One [Member] |  |
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items] |  |
Leverage ratio | 0.085 |
Tier One Leverage Capital to Average Assets | 0.085 |
Covid 19[Member] | From Two Thousand And Twenty Two Onwards [Member] |  |
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items] |  |
Leverage ratio | 0.09 |
Tier One Leverage Capital to Average Assets | 0.09 |
Minimum [Member] |  |
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items] |  |
Leverage ratio |  | 0.08
Tier One Leverage Capital to Average Assets |  | 0.08
Maximum [Member] |  |
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items] |  |
Leverage ratio |  | 0.09
Tier One Leverage Capital to Average Assets |  | 0.09

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- Definition Ratio of Tier 1 capital to average assets as defined by regulatory framework. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=117337116&loc=SL5958568-112826 + Details
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