National Storage Affiliates Trust Annual report pursuant to Section 13 and 15(d)

DEBT FINANCING - Debt Summary (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Principal amount	$ 954,991	$ 873,194
Unamortized debt issuance costs and debt premium, net	3,106	5,760
Total debt	$ 958,097	$ 878,954
Line of Credit [Member] \| Credit Facility [Member] \| Revolving line of credit [Member]
Debt Instrument [Line Items]
Effective interest rate (percent)	2.96%	2.17%
Principal amount	$ 88,500	$ 246,500
Unsecured Debt [Member] \| Credit Facility [Member] \| Tranche A Term Loan [Member]
Debt Instrument [Line Items]
Effective interest rate (percent)	2.63%
Principal amount	$ 235,000	225,000
Unsecured Debt [Member] \| Credit Facility [Member] \| Tranche B Term Loan [Member]
Debt Instrument [Line Items]
Effective interest rate (percent)	3.24%
Principal amount	$ 155,000	100,000
Unsecured Debt [Member] \| Credit Facility [Member] \| Tranche C Term Loan [Member]
Debt Instrument [Line Items]
Effective interest rate (percent)	3.71%
Principal amount	$ 105,000	0
Unsecured Debt [Member] \| Term Loan Facility [Member]
Debt Instrument [Line Items]
Effective interest rate (percent)	3.08%
Principal amount	$ 100,000	100,000
Mortgages [Member] \| Fixed Rate Mortgages [Member]
Debt Instrument [Line Items]
Effective interest rate (percent)	4.15%
Principal amount	$ 271,491	$ 201,694