Quarterly report pursuant to Section 13 or 15(d)

DEBT FINANCING - Debt Summary (Details)

v2.4.1.9
DEBT FINANCING - Debt Summary (Details) (USD $)
In Thousands, unless otherwise specified
Mar. 31, 2015
Dec. 31, 2014
Debt Instrument [Line Items]    
Debt financing $ 618,290us-gaap_DebtLongtermAndShorttermCombinedAmount $ 597,691us-gaap_DebtLongtermAndShorttermCombinedAmount
Related Party Note [Member]    
Debt Instrument [Line Items]    
Debt financing 4,054us-gaap_DebtLongtermAndShorttermCombinedAmount
/ us-gaap_DebtInstrumentAxis
= nsa_RelatedPartyNoteMember
0us-gaap_DebtLongtermAndShorttermCombinedAmount
/ us-gaap_DebtInstrumentAxis
= nsa_RelatedPartyNoteMember
Effective interest rate 3.30%us-gaap_DebtInstrumentInterestRateEffectivePercentage
/ us-gaap_DebtInstrumentAxis
= nsa_RelatedPartyNoteMember
 
Line of Credit [Member] | Credit Facility [Member] | Revolving line of credit [Member]    
Debt Instrument [Line Items]    
Debt financing 182,217us-gaap_DebtLongtermAndShorttermCombinedAmount
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_DebtInstrumentAxis
= nsa_CreditFacilityMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_LineOfCreditMember
166,217us-gaap_DebtLongtermAndShorttermCombinedAmount
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_DebtInstrumentAxis
= nsa_CreditFacilityMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_LineOfCreditMember
Effective interest rate 2.78%us-gaap_DebtInstrumentInterestRateEffectivePercentage
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_DebtInstrumentAxis
= nsa_CreditFacilityMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_LineOfCreditMember
 
Line of Credit [Member] | Credit Facility [Member] | Term Loan [Member]    
Debt Instrument [Line Items]    
Debt financing 144,558us-gaap_DebtLongtermAndShorttermCombinedAmount
/ us-gaap_CreditFacilityAxis
= nsa_TermLoanMember
/ us-gaap_DebtInstrumentAxis
= nsa_CreditFacilityMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_LineOfCreditMember
144,558us-gaap_DebtLongtermAndShorttermCombinedAmount
/ us-gaap_CreditFacilityAxis
= nsa_TermLoanMember
/ us-gaap_DebtInstrumentAxis
= nsa_CreditFacilityMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_LineOfCreditMember
Effective interest rate 3.65%us-gaap_DebtInstrumentInterestRateEffectivePercentage
/ us-gaap_CreditFacilityAxis
= nsa_TermLoanMember
/ us-gaap_DebtInstrumentAxis
= nsa_CreditFacilityMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_LineOfCreditMember
 
Loans Payable [Member] | Unsecured Term Loan [Member]    
Debt Instrument [Line Items]    
Debt financing 50,000us-gaap_DebtLongtermAndShorttermCombinedAmount
/ us-gaap_DebtInstrumentAxis
= nsa_UnsecuredTermLoanMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_LoansPayableMember
50,000us-gaap_DebtLongtermAndShorttermCombinedAmount
/ us-gaap_DebtInstrumentAxis
= nsa_UnsecuredTermLoanMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_LoansPayableMember
Effective interest rate 5.18%us-gaap_DebtInstrumentInterestRateEffectivePercentage
/ us-gaap_DebtInstrumentAxis
= nsa_UnsecuredTermLoanMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_LoansPayableMember
 
Mortgages [Member] | Fixed Rate Mortgages [Member]    
Debt Instrument [Line Items]    
Debt financing 153,961us-gaap_DebtLongtermAndShorttermCombinedAmount
/ us-gaap_DebtInstrumentAxis
= nsa_FixedRateMortgagesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_MortgagesMember
153,416us-gaap_DebtLongtermAndShorttermCombinedAmount
/ us-gaap_DebtInstrumentAxis
= nsa_FixedRateMortgagesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_MortgagesMember
Effective interest rate 4.07%us-gaap_DebtInstrumentInterestRateEffectivePercentage
/ us-gaap_DebtInstrumentAxis
= nsa_FixedRateMortgagesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_MortgagesMember
 
Mortgages [Member] | Variable Rate Mortgages [Member]    
Debt Instrument [Line Items]    
Debt financing $ 83,500us-gaap_DebtLongtermAndShorttermCombinedAmount
/ us-gaap_DebtInstrumentAxis
= nsa_VariableRateMortgagesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_MortgagesMember
$ 83,500us-gaap_DebtLongtermAndShorttermCombinedAmount
/ us-gaap_DebtInstrumentAxis
= nsa_VariableRateMortgagesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_MortgagesMember
Effective interest rate 4.69%us-gaap_DebtInstrumentInterestRateEffectivePercentage
/ us-gaap_DebtInstrumentAxis
= nsa_VariableRateMortgagesMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_MortgagesMember