Quarterly report pursuant to Section 13 or 15(d)

SUBSEQUENT EVENTS - Debt (Details)

v2.4.1.9
SUBSEQUENT EVENTS - Debt (Details) (USD $)
In Thousands, unless otherwise specified
2 Months Ended
Jun. 05, 2015
Mar. 31, 2015
Loans Payable [Member] | Unsecured Term Loan [Member]    
Extinguishment of Debt [Line Items]    
Effective interest rate   5.18%us-gaap_DebtInstrumentInterestRateEffectivePercentage
/ us-gaap_DebtInstrumentAxis
= nsa_UnsecuredTermLoanMember
/ us-gaap_ExtinguishmentOfDebtAxis
= us-gaap_LoansPayableMember
Mortgages [Member] | US Bank senior term loan [Member]    
Extinguishment of Debt [Line Items]    
Effective interest rate   2.58%us-gaap_DebtInstrumentInterestRateEffectivePercentage
/ us-gaap_DebtInstrumentAxis
= nsa_SeniorTermLoanOneMember
/ us-gaap_ExtinguishmentOfDebtAxis
= us-gaap_MortgagesMember
Mortgages [Member] | US Bank senior term loan [Member]    
Extinguishment of Debt [Line Items]    
Effective interest rate   2.43%us-gaap_DebtInstrumentInterestRateEffectivePercentage
/ us-gaap_DebtInstrumentAxis
= nsa_SeniorTermLoanTwoMember
/ us-gaap_ExtinguishmentOfDebtAxis
= us-gaap_MortgagesMember
Mortgages [Member] | Mezzanine loan [Member]    
Extinguishment of Debt [Line Items]    
Effective interest rate   9.65%us-gaap_DebtInstrumentInterestRateEffectivePercentage
/ us-gaap_DebtInstrumentAxis
= nsa_MezzanineLoanMember
/ us-gaap_ExtinguishmentOfDebtAxis
= us-gaap_MortgagesMember
Line of Credit [Member] | Revolving line of credit [Member]    
Extinguishment of Debt [Line Items]    
Effective interest rate   2.78%us-gaap_DebtInstrumentInterestRateEffectivePercentage
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_ExtinguishmentOfDebtAxis
= us-gaap_LineOfCreditMember
Subsequent Event [Member]    
Extinguishment of Debt [Line Items]    
Extinguishment of debt, principal $ 229,800us-gaap_ExtinguishmentOfDebtAmount
/ us-gaap_SubsequentEventTypeAxis
= us-gaap_SubsequentEventMember
 
Extinguishment of debt, prepayment penalty 500nsa_ExtinguishmentOfDebtPrepaymentPenalty
/ us-gaap_SubsequentEventTypeAxis
= us-gaap_SubsequentEventMember
 
Extinguishment of debt, write-off of debt issuance costs 414us-gaap_WriteOffOfDeferredDebtIssuanceCost
/ us-gaap_SubsequentEventTypeAxis
= us-gaap_SubsequentEventMember
 
Subsequent Event [Member] | Loans Payable [Member] | Unsecured Term Loan [Member]    
Extinguishment of Debt [Line Items]    
Extinguishment of debt, principal 50,000us-gaap_ExtinguishmentOfDebtAmount
/ us-gaap_DebtInstrumentAxis
= nsa_UnsecuredTermLoanMember
/ us-gaap_ExtinguishmentOfDebtAxis
= us-gaap_LoansPayableMember
/ us-gaap_SubsequentEventTypeAxis
= us-gaap_SubsequentEventMember
 
Extinguishment of debt, write-off of debt issuance costs 219us-gaap_WriteOffOfDeferredDebtIssuanceCost
/ us-gaap_DebtInstrumentAxis
= nsa_UnsecuredTermLoanMember
/ us-gaap_ExtinguishmentOfDebtAxis
= us-gaap_LoansPayableMember
/ us-gaap_SubsequentEventTypeAxis
= us-gaap_SubsequentEventMember
 
Subsequent Event [Member] | Mortgages [Member] | Variable Rate Mortgages [Member]    
Extinguishment of Debt [Line Items]    
Extinguishment of debt, principal 83,500us-gaap_ExtinguishmentOfDebtAmount
/ us-gaap_DebtInstrumentAxis
= nsa_VariableRateMortgagesMember
/ us-gaap_ExtinguishmentOfDebtAxis
= us-gaap_MortgagesMember
/ us-gaap_SubsequentEventTypeAxis
= us-gaap_SubsequentEventMember
 
Extinguishment of debt, prepayment penalty 500nsa_ExtinguishmentOfDebtPrepaymentPenalty
/ us-gaap_DebtInstrumentAxis
= nsa_VariableRateMortgagesMember
/ us-gaap_ExtinguishmentOfDebtAxis
= us-gaap_MortgagesMember
/ us-gaap_SubsequentEventTypeAxis
= us-gaap_SubsequentEventMember
 
Extinguishment of debt, write-off of debt issuance costs 195us-gaap_WriteOffOfDeferredDebtIssuanceCost
/ us-gaap_DebtInstrumentAxis
= nsa_VariableRateMortgagesMember
/ us-gaap_ExtinguishmentOfDebtAxis
= us-gaap_MortgagesMember
/ us-gaap_SubsequentEventTypeAxis
= us-gaap_SubsequentEventMember
 
Subsequent Event [Member] | Mortgages [Member] | US Bank senior term loan [Member]    
Extinguishment of Debt [Line Items]    
Extinguishment of debt, principal 52,000us-gaap_ExtinguishmentOfDebtAmount
/ us-gaap_DebtInstrumentAxis
= nsa_SeniorTermLoanOneMember
/ us-gaap_ExtinguishmentOfDebtAxis
= us-gaap_MortgagesMember
/ us-gaap_SubsequentEventTypeAxis
= us-gaap_SubsequentEventMember
 
Extinguishment of debt, write-off of debt issuance costs 137us-gaap_WriteOffOfDeferredDebtIssuanceCost
/ us-gaap_DebtInstrumentAxis
= nsa_SeniorTermLoanOneMember
/ us-gaap_ExtinguishmentOfDebtAxis
= us-gaap_MortgagesMember
/ us-gaap_SubsequentEventTypeAxis
= us-gaap_SubsequentEventMember
 
Subsequent Event [Member] | Mortgages [Member] | US Bank senior term loan [Member]    
Extinguishment of Debt [Line Items]    
Extinguishment of debt, principal 6,500us-gaap_ExtinguishmentOfDebtAmount
/ us-gaap_DebtInstrumentAxis
= nsa_SeniorTermLoanTwoMember
/ us-gaap_ExtinguishmentOfDebtAxis
= us-gaap_MortgagesMember
/ us-gaap_SubsequentEventTypeAxis
= us-gaap_SubsequentEventMember
 
Extinguishment of debt, write-off of debt issuance costs 16us-gaap_WriteOffOfDeferredDebtIssuanceCost
/ us-gaap_DebtInstrumentAxis
= nsa_SeniorTermLoanTwoMember
/ us-gaap_ExtinguishmentOfDebtAxis
= us-gaap_MortgagesMember
/ us-gaap_SubsequentEventTypeAxis
= us-gaap_SubsequentEventMember
 
Subsequent Event [Member] | Mortgages [Member] | Mezzanine loan [Member]    
Extinguishment of Debt [Line Items]    
Extinguishment of debt, principal 25,000us-gaap_ExtinguishmentOfDebtAmount
/ us-gaap_DebtInstrumentAxis
= nsa_MezzanineLoanMember
/ us-gaap_ExtinguishmentOfDebtAxis
= us-gaap_MortgagesMember
/ us-gaap_SubsequentEventTypeAxis
= us-gaap_SubsequentEventMember
 
Extinguishment of debt, prepayment penalty 500nsa_ExtinguishmentOfDebtPrepaymentPenalty
/ us-gaap_DebtInstrumentAxis
= nsa_MezzanineLoanMember
/ us-gaap_ExtinguishmentOfDebtAxis
= us-gaap_MortgagesMember
/ us-gaap_SubsequentEventTypeAxis
= us-gaap_SubsequentEventMember
 
Extinguishment of debt, write-off of debt issuance costs 42us-gaap_WriteOffOfDeferredDebtIssuanceCost
/ us-gaap_DebtInstrumentAxis
= nsa_MezzanineLoanMember
/ us-gaap_ExtinguishmentOfDebtAxis
= us-gaap_MortgagesMember
/ us-gaap_SubsequentEventTypeAxis
= us-gaap_SubsequentEventMember
 
Subsequent Event [Member] | Line of Credit [Member] | Revolving line of credit [Member]    
Extinguishment of Debt [Line Items]    
Extinguishment of debt, principal $ 96,300us-gaap_ExtinguishmentOfDebtAmount
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_ExtinguishmentOfDebtAxis
= us-gaap_LineOfCreditMember
/ us-gaap_SubsequentEventTypeAxis
= us-gaap_SubsequentEventMember