Commitments and Contingencies (Details Textual) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012
Commitments To Fund Loans	$ 63.6
Maximum [Member]
Loans Receivables With Fixed Rates Of Interest	17.00%
Minimum [Member]
Loans Receivables With Fixed Rates Of Interest	3.25%

Reflects the carrying amount of loans charging borrowers fixed rates of interest.

No definition available.

Name:	nvsl_LoansReceivablesWithFixedRatesOfInterest
Namespace Prefix:	nvsl_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant