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

Annual report pursuant to Section 13 and 15(d)

SUBSEQUENT EVENTS - Credit Facility Increase (Details)

SUBSEQUENT EVENTS - Credit Facility Increase (Details) - Subsequent Event [Member]	Jan. 29, 2018 USD ($)
Unsecured Debt [Member] \| Amended Credit Facility [Member]
Subsequent Event [Line Items]
Current borrowing capacity	$ 1,000,000,000
Maximum borrowing capacity	1,300,000,000
Unsecured Debt [Member] \| Amended Credit Facility [Member] \| Tranche D Term Loan [Member]
Subsequent Event [Line Items]
Debt instrument, face amount	125,000,000.00
Credit facility expansion	$ 20,000,000
Unsecured Debt [Member] \| Amended Credit Facility [Member] \| Tranche D Term Loan [Member] \| Federal Funds Effective Swap Rate [Member]
Subsequent Event [Line Items]
Borrowing rate spread (percent)	0.50%
Unsecured Debt [Member] \| Amended Credit Facility [Member] \| Tranche D Term Loan [Member] \| LIBOR [Member]
Subsequent Event [Line Items]
Borrowing rate spread (percent)	1.00%
Unsecured Debt [Member] \| Amended Credit Facility [Member] \| Tranche D Term Loan [Member] \| LIBOR [Member] \| Minimum [Member]
Subsequent Event [Line Items]
Leverage based margin threshold (percent)	1.30%
Elective leverage based margin threshold (percent)	0.90%
Unsecured Debt [Member] \| Amended Credit Facility [Member] \| Tranche D Term Loan [Member] \| LIBOR [Member] \| Maximum [Member]
Subsequent Event [Line Items]
Leverage based margin threshold (percent)	1.85%
Elective leverage based margin threshold (percent)	1.75%
Unsecured Debt [Member] \| Amended Credit Facility [Member] \| Tranche D Term Loan [Member] \| Base Rate [Member] \| Minimum [Member]
Subsequent Event [Line Items]
Leverage based margin threshold (percent)	0.30%
Elective leverage based margin threshold (percent)	0.00%
Unsecured Debt [Member] \| Amended Credit Facility [Member] \| Tranche D Term Loan [Member] \| Base Rate [Member] \| Maximum [Member]
Subsequent Event [Line Items]
Leverage based margin threshold (percent)	0.85%
Elective leverage based margin threshold (percent)	0.75%
Unsecured Debt [Member] \| Amended Credit Facility [Member] \| Tranche A Term Loan [Member]
Subsequent Event [Line Items]
Maximum borrowing capacity	$ 235,000,000
Unsecured Debt [Member] \| Amended Credit Facility [Member] \| Tranche B Term Loan [Member]
Subsequent Event [Line Items]
Maximum borrowing capacity	155,000,000
Unsecured Debt [Member] \| Amended Credit Facility [Member] \| Tranche C Term Loan [Member]
Subsequent Event [Line Items]
Maximum borrowing capacity	105,000,000
Unsecured Debt [Member] \| Expansion Option Of Amended Credit Facility [Member]
Subsequent Event [Line Items]
Current borrowing capacity	300,000,000.0
Line of Credit [Member] \| Amended Credit Facility [Member] \| Revolving line of credit [Member]
Subsequent Event [Line Items]
Maximum borrowing capacity	$ 400,000,000