LOANS RECEIVABLE (Details 7) $ in Thousands	6 Months Ended
Jun. 30, 2015 USD ($)	Jun. 30, 2014 USD ($)
Financing Receivable, Modifications [Line Items]
Number of Loans	1	7
Pre-Modification Recorded Investment	$ 53	$ 511
Post-Modification Recorded Investment	$ 53	$ 511
Percentage Of Reduced Interest Rate		100.00%
Percentage Of Financing Receivable Modifications	100.00%
Deferred Principal Payments [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans		2
Pre-Modification Recorded Investment		$ 348
Post-Modification Recorded Investment		$ 348
Percentage Of Reduced Interest Rate		68.10%
Extended Payment Terms [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	1	1
Pre-Modification Recorded Investment	$ 53	$ 98
Post-Modification Recorded Investment	$ 53	$ 98
Percentage Of Reduced Interest Rate		19.20%
Percentage Of Extension of Payment Terms	100.00%
Below Market Interest Rate [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans		4
Pre-Modification Recorded Investment		$ 65
Post-Modification Recorded Investment		$ 65
Percentage Of Reduced Interest Rate		12.70%
One to four family [Member] \| Deferred Principal Payments [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans		2
Pre-Modification Recorded Investment		$ 348
Post-Modification Recorded Investment		$ 348
Percentage Of Reduced Interest Rate		68.10%
One to four family [Member] \| Below Market Interest Rate [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans		1
Pre-Modification Recorded Investment		$ 35
Post-Modification Recorded Investment		$ 35
Percentage Of Reduced Interest Rate		6.80%
Commercial Business Loans [Member] \| Extended Payment Terms [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	1	1
Pre-Modification Recorded Investment	$ 53	$ 98
Post-Modification Recorded Investment	$ 53	$ 98
Percentage Of Reduced Interest Rate		19.20%
Percentage Of Extension of Payment Terms	100.00%
Commercial Business Loans [Member] \| Below Market Interest Rate [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans		2
Pre-Modification Recorded Investment		$ 20
Post-Modification Recorded Investment		$ 20
Percentage Of Reduced Interest Rate		3.90%
Commercial real estate loans [Member] \| Below Market Interest Rate [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans		1
Pre-Modification Recorded Investment		$ 10
Post-Modification Recorded Investment		$ 10
Percentage Of Reduced Interest Rate		2.00%

Represents the percentage of extension of payment terms during the period

No definition available.

Name:	nvsl_PercentageOfExtensionOfPaymentTerms
Namespace Prefix:	nvsl_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the total percentage of financing receivable modification during the period.

+ References

No definition available.

+ Details

Name:	nvsl_PercentageOfFinancingReceivableModifications
Namespace Prefix:	nvsl_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the percentage of reduction interest rate in financial receivable.

+ References

No definition available.

+ Details

Name:	nvsl_PercentageOfReducedInterestRate
Namespace Prefix:	nvsl_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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

- Definition

Number of financing receivables that have been modified by troubled debt restructurings.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 33

-URI http://asc.fasb.org/extlink&oid=49124121&loc=SL6953676-111524

+ Details

Name:	us-gaap_FinancingReceivableModificationsNumberOfContracts2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Post-modification amount of investment in financing receivables modified by troubled debt restructurings.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Pre-modification amount of investment in financing receivables modified by troubled debt restructurings.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_StatementEquityComponentsAxis=nvsl_DeferredPrincipalPaymentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	nvsl_FinancingReceivablePaymentTermsAxis=nvsl_ExtendedPaymentTermsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=nvsl_BelowMarketInterestRateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=nvsl_OneToFourFamilyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_FinancialInstrumentAxis=nvsl_CommercialRealEstateLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: