LOANS AND ALLOWANCE FOR CREDIT LOSSES FOR LOANS - Risk category of bank loans by year of origination (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
Sep. 30, 2024	Sep. 30, 2023	Mar. 31, 2024
Origination year
2025/2024	$ 43,051		$ 68,625
2024/2023	85,553		169,408
2023/2022	173,210		338,864
2022/2021	332,659		126,861
2021/2020	122,016		84,175
Prior	277,479		215,697
Revolving Loans	27,009		20,383
Total Loans Receivable	1,060,977		1,024,013
Gross write-offs
2024/2023			11
Prior			2
Revolving Loans	1
Total Loans Receivable	1	$ 11	13
Commercial and Industrial \| Commercial Business
Origination year
2025/2024	7,139		14,126
2024/2023	19,349		63,838
2023/2022	63,809		85,864
2022/2021	82,690		28,119
2021/2020	25,275		17,431
Prior	27,148		12,701
Revolving Loans	11,485		7,325
Total Loans Receivable	236,895		229,404
Commercial Real Estate Portfolio Segment
Origination year
Total Loans Receivable	947,832		925,907
Commercial Real Estate Portfolio Segment \| Commercial Business
Origination year
Total Loans Receivable	236,895		229,404
Commercial Real Estate Portfolio Segment \| Commercial Real Estate
Origination year
2025/2024	13,317		36,636
2024/2023	39,621		70,599
2023/2022	65,591		147,912
2022/2021	145,808		89,662
2021/2020	88,164		53,424
Prior	220,954		185,268
Total Loans Receivable	573,455		583,501
Commercial Real Estate Portfolio Segment \| Land
Origination year
2025/2024	622		2,361
2024/2023	3,463		2,695
2023/2022	2,622		94
2022/2021	89
2021/2020			106
Prior	500		437
Revolving Loans	(22)
Total Loans Receivable	7,274		5,693
Commercial Real Estate Portfolio Segment \| Multi-Family
Origination year
2025/2024	84		970
2024/2023	959		21,643
2023/2022	26,280		32,003
2022/2021	36,088		4,841
2021/2020	4,418		8,823
Prior	10,881		2,491
Total Loans Receivable	78,710		70,771
Commercial Real Estate Portfolio Segment \| Real Estate Construction
Origination year
2025/2024	7,361		14,114
2024/2023	21,551		10,078
2023/2022	14,466		12,346
2022/2021	8,120
Total Loans Receivable	51,498		36,538
Consumer
Origination year
Total Loans Receivable	113,145		98,106
Gross write-offs
Total Loans Receivable	1	$ 11
Consumer \| Real estate one-to-four family
Origination year
2025/2024	11
2023/2022			60,447
2022/2021	59,710		4,164
2021/2020	4,101		4,364
Prior	17,981		14,792
Revolving Loans	15,108		12,599
Total Loans Receivable	96,911		96,366
Consumer \| Other installment
Origination year
2025/2024	14,517		418
2024/2023	610		555
2023/2022	442		198
2022/2021	154		75
2021/2020	58		27
Prior	15		8
Revolving Loans	438		459
Total Loans Receivable	16,234		1,740
Gross write-offs
2024/2023			11
Prior			2
Revolving Loans	1
Total Loans Receivable	1		13
Pass
Origination year
2025/2024	37,929		67,311
2024/2023	82,306		165,301
2023/2022	166,753		337,234
2022/2021	331,121		126,861
2021/2020	121,386		83,654
Prior	244,718		188,352
Revolving Loans	25,772		17,885
Total Loans Receivable	1,009,985		986,598
Pass \| Commercial and Industrial \| Commercial Business
Origination year
2025/2024	7,139		14,126
2024/2023	19,349		63,838
2023/2022	61,559		85,131
2022/2021	82,037		28,119
2021/2020	24,663		16,945
Prior	26,164		12,411
Revolving Loans	10,248		4,827
Total Loans Receivable	231,159		225,397
Pass \| Commercial Real Estate Portfolio Segment \| Commercial Real Estate
Origination year
2025/2024	8,820		36,116
2024/2023	36,374		66,847
2023/2022	61,894		147,015
2022/2021	144,923		89,662
2021/2020	88,164		53,424
Prior	189,444		158,311
Total Loans Receivable	529,619		551,375
Pass \| Commercial Real Estate Portfolio Segment \| Land
Origination year
2025/2024	622		2,361
2024/2023	3,463		2,340
2023/2022	2,297		94
2022/2021	89
2021/2020			106
Prior	500		437
Revolving Loans	(22)
Total Loans Receivable	6,949		5,338
Pass \| Commercial Real Estate Portfolio Segment \| Multi-Family
Origination year
2025/2024	84		970
2024/2023	959		21,643
2023/2022	26,095		32,003
2022/2021	36,088		4,841
2021/2020	4,400		8,788
Prior	10,647		2,429
Total Loans Receivable	78,273		70,674
Pass \| Commercial Real Estate Portfolio Segment \| Real Estate Construction
Origination year
2025/2024	6,736		13,320
2024/2023	21,551		10,078
2023/2022	14,466		12,346
2022/2021	8,120
Total Loans Receivable	50,873		35,744
Pass \| Consumer \| Real estate one-to-four family
Origination year
2025/2024	11
2023/2022			60,447
2022/2021	59,710		4,164
2021/2020	4,101		4,364
Prior	17,948		14,756
Revolving Loans	15,108		12,599
Total Loans Receivable	96,878		96,330
Pass \| Consumer \| Other installment
Origination year
2025/2024	14,517		418
2024/2023	610		555
2023/2022	442		198
2022/2021	154		75
2021/2020	58		27
Prior	15		8
Revolving Loans	438		459
Total Loans Receivable	16,234		1,740
Special Mention
Origination year
2025/2024	5,122		794
2024/2023	3,137		4,107
2023/2022	6,457		1,630
2022/2021	1,538
2021/2020	630		521
Prior	32,545		27,142
Revolving Loans	1,237		2,498
Total Loans Receivable	50,666		36,692
Special Mention \| Commercial and Industrial \| Commercial Business
Origination year
2023/2022	2,250		733
2022/2021	653
2021/2020	612		486
Prior	936		232
Revolving Loans	1,237		2,498
Total Loans Receivable	5,688		3,949
Special Mention \| Commercial Real Estate Portfolio Segment
Origination year
2024/2023			3,752
2023/2022			897
Prior			26,878
Total Loans Receivable			31,527
Special Mention \| Commercial Real Estate Portfolio Segment \| Commercial Real Estate
Origination year
2025/2024	4,497
2024/2023	3,137
2023/2022	3,697
2022/2021	885
Prior	31,442
Total Loans Receivable	43,658
Special Mention \| Commercial Real Estate Portfolio Segment \| Land
Origination year
2024/2023			355
2023/2022	325
Total Loans Receivable	325		355
Special Mention \| Commercial Real Estate Portfolio Segment \| Multi-Family
Origination year
2023/2022	185
2021/2020	18		35
Prior	167		32
Total Loans Receivable	370		67
Special Mention \| Commercial Real Estate Portfolio Segment \| Real Estate Construction
Origination year
2025/2024	625		794
Total Loans Receivable	625		794
Substandard
Origination year
2025/2024			520
2024/2023	110
Prior	216		203
Total Loans Receivable	326		723
Substandard \| Commercial and Industrial \| Commercial Business
Origination year
Prior	48		58
Total Loans Receivable	48		58
Substandard \| Commercial Real Estate Portfolio Segment
Origination year
2025/2024			520
Prior			79
Total Loans Receivable			599
Substandard \| Commercial Real Estate Portfolio Segment \| Commercial Real Estate
Origination year
2024/2023	110
Prior	68
Total Loans Receivable	178
Substandard \| Commercial Real Estate Portfolio Segment \| Multi-Family
Origination year
Prior	67		30
Total Loans Receivable	67		30
Substandard \| Consumer \| Real estate one-to-four family
Origination year
Prior	33		36
Total Loans Receivable	$ 33		$ 36

Amortized cost excluding accrued interest, net, of financing receivable that can be withdrawn, repaid, and redrawn.

No definition available.

Name:	rvsb_FinancingReceivableExcludingAccruedInterestRevolvingNet
Namespace Prefix:	rvsb_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount, excluding accrued interest, of decrease in allowance for credit loss on financing receivable from writeoff. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-6

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-13

+ Details

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

- References

No definition available.

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoffByOriginationYearAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amortized cost excluding accrued interest, before allowance for credit loss, of financing receivable. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479344/326-20-45-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 3B
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-3B

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-5

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- References

No definition available.

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLossByOriginationYearAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amortized cost excluding accrued interest, of financing receivable originated more than five years prior to current fiscal year. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 79
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479294/326-20-55-79

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-6

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 3B
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-3B

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestOriginatedMoreThanFiveYearsBeforeCurrentFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount, excluding accrued interest, of writeoff of financing receivable originated more than five years before current fiscal year. Excludes net investment in lease.

+ References

+ Details

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

- Definition

Amortized cost excluding accrued interest, of financing receivable that can be withdrawn, repaid, and redrawn.

+ References

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestRevolving
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount, excluding accrued interest, of writeoff of financing receivable that can be withdrawn, repaid, and redrawn.

+ References

+ Details

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

- Definition

Amortized cost excluding accrued interest, of financing receivable originated four years prior to current fiscal year. Excludes net investment in lease.

+ References

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestYearFiveOriginatedFourYearsBeforeCurrentFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amortized cost excluding accrued interest, of financing receivable originated three years prior to current fiscal year. Excludes net investment in lease.

+ References

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestYearFourOriginatedThreeYearsBeforeCurrentFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amortized cost excluding accrued interest, of financing receivable originated in current fiscal year. Excludes net investment in lease.

+ References

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestYearOneOriginatedCurrentFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amortized cost excluding accrued interest, of financing receivable originated two years prior to current fiscal year. Excludes net investment in lease.

+ References

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestYearThreeOriginatedTwoYearsBeforeCurrentFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amortized cost excluding accrued interest of financing receivable originated in fiscal year prior to current fiscal year. Excludes net investment in lease.

+ References

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestYearTwoOriginatedFiscalYearBeforeCurrentFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount, excluding accrued interest, of writeoff of financing receivable originated in fiscal year before current fiscal year. Excludes net investment in lease.

+ References

+ Details

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

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_CommercialLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialRealEstatePortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_CommercialRealEstateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_LandMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=srt_MultifamilyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_ConstructionLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ConsumerPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=rvsb_RealEstateOneToFourFamilyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=rvsb_OtherInstallmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InternalCreditAssessmentAxis=us-gaap_PassMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InternalCreditAssessmentAxis=us-gaap_SpecialMentionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InternalCreditAssessmentAxis=us-gaap_SubstandardMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: