Fair Value of Financial Instruments - Summary of Range of Effective Yields and Weighted Average Effective Yields of Partnership's Investments (Details)		Sep. 30, 2021	Dec. 31, 2020
Taxable Mortgage Revenue Bonds [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Weighted Average Effective Yields	[1]	6.70%	7.30%
Taxable Mortgage Revenue Bonds [Member] | Effective rate - minimum [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Range of Effective Yields		4.90%	7.10%
Taxable Mortgage Revenue Bonds [Member] | Effective rate - maximum [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Range of Effective Yields		8.00%	7.40%
Bond Purchase Commitment [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Range of Effective Yields			3.50%
Weighted Average Effective Yields	[1]	4.20%	3.50%
Bond Purchase Commitment [Member] | Effective rate - minimum [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Range of Effective Yields		3.50%
Bond Purchase Commitment [Member] | Effective rate - maximum [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Range of Effective Yields		4.90%
Mortgage Revenue Bonds [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Weighted Average Effective Yields	[1]	3.10%	3.00%
Mortgage Revenue Bonds [Member] | Effective rate - minimum [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Range of Effective Yields		0.90%	1.40%
Mortgage Revenue Bonds [Member] | Effective rate - maximum [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Range of Effective Yields		16.60%	13.30%

[1] Weighted by the total principal outstanding of all the respective securities as of the reporting date.