SHAREHOLDERS' EQUITY AND REGULATORY CAPITAL REQUIREMENTS: Compliance with Regulatory Capital Requirements under Banking Regulations (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Mar. 31, 2018
Shareholders Equity And Regulatory Capital Requirements [Abstract]
Total capital to risk weighted assets actual amount	$ 140,062	$ 123,061
Total capital to risk weighted assets actual ratio	16.88%	15.41%
Total capital to risk weighted assets for capital adequacy purposes amount	$ 66,379	$ 63,868
Total capital to risk weighted assets for capital adequacy purposes ratio	8.00%	8.00%
Total capital to risk weighted assets for capital adequacy purposes well capitalized under prompt corrective action amount	$ 82,974	$ 79,835
Total capital to risk weighted assets for capital adequacy purposes well capitalized under prompt corrective action ratio	10.00%	10.00%
Tier 1 to risk weighted assets actual amount	$ 129,671	$ 113,066
Tier 1 to risk weighted assets actual ratio	15.63%	14.16%
Tier 1 to risk weighted assets for capital adequacy purposes amount	$ 49,784	$ 47,901
Tier 1to risk weighted assets for capital adequacy purposes ratio	6.00%	6.00%
Tier 1 to risk weighted assets well capitalized under prompt corrective action amount	$ 66,379	$ 63,868
Tier 1 to risk weighted assets well capitalized under prompt corrective action ratio	8.00%	8.00%
Common equity Tier 1 capital to risk weighted assets actual amount	$ 129,671	$ 113,066
Common equity Tier 1 capital to risk weighted assets actual ratio	15.63%	14.16%
Common equity Tier 1 to risk weighted assets for capital adequacy purposes amount	$ 37,338	$ 35,926
Common equity Tier 1 to risk weighted assets for capital adequacy purposes ratio	4.50%	4.50%
Common equity Tier 1 to risk weighted assets well capitalized under prompt corrective action amount	$ 53,933	$ 51,893
Common equity Tier 1 to risk weighted assets well capitalized under prompt corrective action ratio	6.50%	6.50%
Tier 1 capital leverage to average tangible assets actual amount	$ 129,671	$ 113,066
Tier 1 capital leverage to average tangible assets actual ratio	11.56%	10.26%
Tier 1 capital leverage to average tangible assets for capital adequacy purposes amount	$ 44,874	$ 44,093
Tier 1 capital leverage to average tangible assets for capital adequacy purposes ratio	4.00%	4.00%
Tier 1 capital leverage to average tangible assets well capitalized under prompt corrective action amount	$ 56,092	$ 55,116
Tier 1 capital leverage to average tangible assets well capitalized under prompt corrective action ratio	5.00%	5.00%

Represents the monetary value of Common Equity Tier 1 Capital, as on the indicated date.

No definition available.

Name:	rvsb_CommonEquityTier1Capital
Namespace Prefix:	rvsb_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Represents the monetary value of Common Equity Tier 1 Capital for adequacy, as on the indicated date.

+ References

No definition available.

+ Details

Name:	rvsb_CommonEquityTier1CapitalForAdequacy
Namespace Prefix:	rvsb_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Represents the ratio of common equity Tier 1 Capital for adequacy to Risk-weighted Assets, as of the indicated date.

+ References

No definition available.

+ Details

Name:	rvsb_CommonEquityTier1CapitalForAdequacyToRiskWeightedAssets
Namespace Prefix:	rvsb_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the monetary value of Common Equity Tier 1 Capital for adequacy, as on the indicated date.

+ References

No definition available.

+ Details

Name:	rvsb_CommonEquityTier1CapitalRequiredToBeWellCapitalized
Namespace Prefix:	rvsb_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Represents the ratio of common equity Tier 1 Capital to be well capitalized, to Risk-weighted Assets, as of the indicated date.

+ References

No definition available.

+ Details

Name:	rvsb_CommonEquityTier1CapitalToBeWellCapitalizedToRiskWeightedAssets
Namespace Prefix:	rvsb_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the ration of common equity Tier 1 Capital to Risk-weighted Assets, as of the indicated date.

+ References

No definition available.

+ Details

Name:	rvsb_CommonEquityTier1CapitalToRiskWeightedAssets
Namespace Prefix:	rvsb_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- References

No definition available.

+ Details

Name:	rvsb_ShareholdersEquityAndRegulatoryCapitalRequirementsAbstract
Namespace Prefix:	rvsb_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of total capital as defined in the regulations.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 948
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=6490092&loc=d3e47304-110998

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1H
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=84167132&loc=d3e65071-112826

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 948
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=6490092&loc=d3e47080-110998

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1H
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=84167132&loc=d3e65071-112826

+ Details

Name:	us-gaap_Capital
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The minimum amount of Total Capital required for capital adequacy purposes under the regulatory framework for prompt corrective action.

+ References

+ Details

Name:	us-gaap_CapitalRequiredForCapitalAdequacy
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The minimum Total risk based capital ratio (total capital divided by risk weighted assets) required for capital adequacy purposes under the regulatory framework for prompt corrective action.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=84167132&loc=SL5958568-112826

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=84167132&loc=SL5958570-112826

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1H
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=84167132&loc=d3e65071-112826

+ Details

Name:	us-gaap_CapitalRequiredForCapitalAdequacyToRiskWeightedAssets
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The amount of Total Capital required to be categorized as well as capitalized under the regulatory framework for prompt corrective action.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=84167132&loc=SL5958568-112826

+ Details

Name:	us-gaap_CapitalRequiredToBeWellCapitalized
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The Total risk based capital ratio (total capital divided by risk weighted assets) required to be categorized as "well capitalized", in the regulatory framework for prompt corrective action.

+ References

+ Details

Name:	us-gaap_CapitalRequiredToBeWellCapitalizedToRiskWeightedAssets
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Total Capital divided by risk weighted assets as defined in the regulations.

+ References

+ Details

Name:	us-gaap_CapitalToRiskWeightedAssets
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Tier 1 Leverage Capital as defined in the regulations. Also called Core Capital.

+ References

+ Details

Name:	us-gaap_TierOneLeverageCapital
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The minimum amount of Tier 1 Leverage Capital required for capital adequacy purposes under the regulatory framework for prompt corrective action.

+ References

+ Details

Name:	us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacy
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The minimum amount of Tier 1 Leverage Capital for capital adequacy purposes divided by average assets as defined in the regulations.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1H
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=84167132&loc=d3e65071-112826

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=84167132&loc=SL5958570-112826

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=84167132&loc=SL5958568-112826

+ Details

Name:	us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacyToAverageAssets
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The amount of Tier 1 Leverage Capital required to be categorized as well capitalized under the regulatory framework for prompt corrective action.

+ References

+ Details

Name:	us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalized
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The amount of Tier 1 Leverage Capital required to be categorized as well capitalized divided by average assets as defined in the regulatory framework for prompt corrective action.

+ References

+ Details

Name:	us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalizedToAverageAssets
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Tier 1 Leverage Capital divided by average assets as defined in the regulations.

+ References

+ Details

Name:	us-gaap_TierOneLeverageCapitalToAverageAssets
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Tier 1 Risk Based Capital as defined in the regulations.

+ References

+ Details

Name:	us-gaap_TierOneRiskBasedCapital
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The minimum amount of Tier 1 Risk Based Capital required for capital adequacy purposes under the regulatory framework for prompt corrective action.

+ References

+ Details

Name:	us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacy
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The minimum Tier One Capital Ratio (Tier one capital divided by risk-weighted assets) required for capital adequacy purposes under the regulatory framework for prompt corrective action.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=84167132&loc=SL5958570-112826

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=84167132&loc=SL5958568-112826

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1H
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=84167132&loc=d3e65071-112826

+ Details

Name:	us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacyToRiskWeightedAssets
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The amount of Tier 1 Risk Based Capital required to be categorized as well capitalized under the regulatory framework for prompt corrective action.

+ References

+ Details

Name:	us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalized
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The Tier 1 capital ratio (Tier 1 capital divided by risk weighted assets) required to be categorized as "well capitalized" under the regulatory framework for prompt corrective action.

+ References

+ Details

Name:	us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalizedToRiskWeightedAssets
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Tier 1 capital divided by risk weighted assets as defined by regulations.

+ References

+ Details

Name:	us-gaap_TierOneRiskBasedCapitalToRiskWeightedAssets
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant