Low Income housing tax credit - Additional Information (Details) - USD ($)	12 Months Ended
Mar. 31, 2024	Mar. 31, 2023
Investments in Affordable Housing Projects [Abstract]
Impairment	$ 0	$ 0

Amount of write-down from impairment of an investment in a qualified affordable housing project.

Reference 1: http://www.xbrl.org/2003/role/recommendedDisclosureRef
-Topic 323
-SubTopic 740
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481543/323-740-50-2

Name:	us-gaap_AffordableHousingProjectInvestmentWriteDownAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration