Accounting Policies, by Policy (Policies)	3 Months Ended	9 Months Ended
	Mar. 31, 2022	Sep. 30, 2021
Accounting Policies [Abstract]
Key Provisions of Operating or Partnership Agreement, Description	AEI Net Lease Income & Growth Fund XX Limited Partnership (“Partnership”) was formed to acquire and lease commercial properties to operating tenants. The Partnership's operations are managed by AEI Fund Management XX, Inc. (“AFM”), the Managing General Partner. The Estate of Robert P. Johnson serves as the Individual General Partner. AFM is a wholly owned subsidiary of AEI Capital Corporation of which the Robert P. Johnson Trust and Patricia Johnson, own a majority interest. AEI Fund Management, Inc. (“AEI”), an affiliate of AFM, performs the administrative and operating functions for the Partnership. In January 2021, the Managing General Partner mailed a Consent Statement (Proxy) seeking the consent of the Limited Partners to continue the Partnership for an additional 60 months or to initiate the final disposition, liquidation and distribution of all of the Partnership’s properties and assets within 24 to 36 months. Approval of either proposal required the affirmative vote of holders of a majority of the outstanding units. On March 3, 2021, the proposal was approved with a majority of Units voting in favor of the proposal. As a result, the Managing General Partner is proceeding with the planned liquidation of the Partnership
New Accounting Pronouncement or Change in Accounting Principle, Description		In April 2020, the Financial Accounting Standards Board (FASB) issued a question-and-answer document (the “Lease Modification Q&A”) focused on the application of lease accounting guidance to lease concessions provided as a result of COVID-19. Under existing lease guidance, the Partnership would have to determine, on a lease by lease basis, if a lease concession was the result of a new arrangement reached with the tenant or if a lease concession was under the enforceable rights and obligations within the existing lease agreement. The Lease Modification Q&A clarifies that entities may elect to not evaluate whether lease-related relief that lessors provide to mitigate the economic effects of COVID-19 on lessees is a lease modification under current lease guidance. Instead, an entity that elects not to evaluate whether a concession directly related to COVID-19 is a modification can then elect whether to apply the modification guidance. Other accounting standards that have been issued or proposed by the FASB are currently not applicable to the Partnership or are not expected to have a significant impact on the Partnership’s financial position, results of operations and cash flows.