Partners' Capital (Details) - USD ($)	3 Months Ended				6 Months Ended
Partners' Capital (Details) - USD ($)	Jun. 30, 2025	Mar. 31, 2025	Jun. 30, 2024	Mar. 31, 2024	Jun. 30, 2025	Jun. 30, 2024
Partners' Capital (Details) [Line Items]
Distribution Made to Limited Partner, Cash Distributions Declared	$ 367,780	$ 173,233	$ 173,233	$ 173,233	$ 541,013	$ 346,466
Distribution Made to Limited Partner, Distributions Declared, Per Unit (in Dollars per share)					$ 32.4
Partners' Capital Account, Units, Redeemed (in Shares)	1,095.87
Partners' Capital Account, Redemptions	$ 795,303
Units of Partnership Interest, Amount (in Shares)	7,953				7,953
Limited Partner [Member]
Partners' Capital (Details) [Line Items]
Distribution Made to Limited Partner, Cash Distributions Declared	$ 364,102	171,501	171,501	171,501	$ 535,603	$ 343,002
Distribution Made to Limited Partner, Distributions Declared, Per Unit (in Dollars per share)						$ 20.09
Weighted Average Limited Partnership Units Outstanding, Basic (in Shares)					16,529	17,077
DistributionsPerUnitOfNetIncome (in Dollars per share)					$ 32.4	$ 20.09
DistributionsPerUnitOfReturnOfCapital (in Dollars per share)					$ 0
Partners' Capital Account, Units, Redeemed (in Shares)	(1,095,870,000)
Partners' Capital Account, Redemptions	$ 787,350
General Partner [Member]
Partners' Capital (Details) [Line Items]
Distribution Made to Limited Partner, Cash Distributions Declared	3,678	$ 1,732	$ 1,732	$ 1,732	$ 5,410	$ 3,464
Partners' Capital Account, Redemptions	$ 7,953

AEI INCOME & GROWTH FUND XXI LTD PARTNERSHIP 10-Q