Related Party Transactions - Additional Information (Detail)			3 Months Ended	9 Months Ended
	Apr. 17, 2020	Mar. 27, 2018	Jun. 30, 2020 USD ($)	Sep. 30, 2020 USD ($) Employee	Sep. 30, 2019 USD ($)
Related Party Transaction [Line Items]
Maximum period for reimbursement of offering cost				60 days
Maximum offering cost rate				3.50%
Number of employees \| Employee				0
Due to affiliates				$ 69,053	$ 114,874
Tenant Programs
Related Party Transaction [Line Items]
Threshold percentage to purchase triggering member ownership interest in joint venture at fair market value		95.00%
Tenant Programs \| TRS subsidiary
Related Party Transaction [Line Items]
Percentage of ownership interest in joint venture		0.10%
Percentage of net revenue generated from tenant insurance to be received under terms of joint venture agreement		0.10%
Private Offering Dealer Manager Agreement
Related Party Transaction [Line Items]
Underwriting compensation				10.00%
Maximum percentage other non-accountable expenses				3.00%
SmartStop Asset Management
Related Party Transaction [Line Items]
Agreement termination notice period	60 days
Class W Common Stock
Related Party Transaction [Line Items]
Percentage of offering cost without reimbursement				1.15%
Class W Common Stock \| Dealer Manager Servicing Fees
Related Party Transaction [Line Items]
Monthly stockholder servicing fee accrual description				accrues daily in an amount equal to 1/365th of 0.5% of the purchase price per share
Monthly serving fee payable and accrues daily percentage				0.50%
Class W Common Stock \| Private Offering Dealer Manager Agreement
Related Party Transaction [Line Items]
Percentage of gross proceeds from sale of shares				10.00%
Maximum dealer manager servicing fee percentage of proceeds from Primary Offering				9.00%
Minimum future dealer manager servicing fee percentage of proceeds from Primary Offering			10.00%
Threshold limit of dealer manager servicing fees included in liability for future payment			10.00%
Due to affiliates			$ 1,600,000
Increase (decrease) in additional paid in capital			$ 1,600,000
Class A Common Stock \| Dealer Manager
Related Party Transaction [Line Items]
Maximum sale commission fees percentage of proceed from Primary Offering				6.00%
Maximum dealer manager commission fee percentage of proceeds from Primary Offering				3.00%
Class A Common Stock \| Private Offering Dealer Manager Agreement
Related Party Transaction [Line Items]
Percentage of gross proceeds from sale of shares				10.00%
Class T Common Stock \| Dealer Manager
Related Party Transaction [Line Items]
Maximum sale commission fees percentage of proceed from Primary Offering				3.00%
Maximum dealer manager commission fee percentage of proceeds from Primary Offering				3.00%
Class T Common Stock \| Stockholder Servicing Fees
Related Party Transaction [Line Items]
Monthly stockholder servicing fee accrual description				accrues daily in an amount equal to 1/365th of 1% of the purchase price per share
Monthly serving fee payable and accrues daily percentage				1.00%
Class T Common Stock \| Private Offering Dealer Manager Agreement
Related Party Transaction [Line Items]
Percentage of gross proceeds from sale of shares				10.00%
Advisory Agreement
Related Party Transaction [Line Items]
Maximum period for reimbursement of offering cost				60 days
Maximum offering cost rate				3.50%
Gross proceeds from Public Offering, threshold percentage of expenses for reimbursement				15.00%
Monthly asset management fee				0.0833%
Monthly asset management fee one twelfth of less than one percentage of asset value payable				one-twelfth of 1%
Operating expenses reimbursement percentage of average investment in assets				2.00%
Operating expenses reimbursement percentage of net income				25.00%
Operating expenses exceed limitation				12 months
Maximum days for disclosure fact				60 days
Advisory Agreement \| Class W Common Stock
Related Party Transaction [Line Items]
Percentage of offering cost without reimbursement				1.15%
Amended Property Management Agreement
Related Party Transaction [Line Items]
Percentage of fee of Property Manager				6.00%
Property management agreement termination description				The property management agreement has a three year term and automatically renews for successive three year periods thereafter, unless we or our Property Manager provide prior written notice at least 90 days prior to the expiration of the term. After the end of the initial three year term, either party may terminate a property management agreement generally upon 60 days prior written notice. With respect to each new property we acquire for which we enter into a property management agreement with our Property Manager we will also pay our Property Manager a one-time start-up fee in the amount of $3,750.
Term of property management agreement				3 years
Renewal term of property management agreement				3 years
Notice period for property management agreement by property manager				60 days
Period of prior written notice for termination of property management agreement				90 days
Percentage of construction management fee				5.00%
Construction management fees for excess of capital improvement work				$ 10,000
Property manager one-time start-up fees				3,750
Amended Property Management Agreement \| Minimum
Related Party Transaction [Line Items]
Property Manager receives fee for services				$ 3,000
Transfer Agent Agreement
Related Party Transaction [Line Items]
Term of property management agreement				3 years
Renewal term of property management agreement				1 year
Period of prior written notice for termination of property management agreement				90 days
Affiliate of Property Manager \| Tenant Programs
Related Party Transaction [Line Items]
Percentage of ownership interest in joint venture		99.90%
Percentage of net revenue generated from tenant insurance to be received under terms of joint venture agreement		99.90%
Tenant insurance revenue				$ 610,000	260,000
Storage Auction Program
Related Party Transaction [Line Items]
Auction fees				$ 8,000	$ 7,000
Ownership Percentage				50.00%

Strategic Storage Trust IV, Inc. 10-Q