CONSOLIDATED STATEMENTS OF CHANGES IN PARTNER'S CAPITAL - USD ($)	3 Months Ended				12 Months Ended			161 Months Ended
	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2020
Increase (Decrease) in Partners' Capital
Balance		$ (37,823,788)		$ (35,624,010)	$ (37,823,788)	$ (35,624,010)	$ (35,315,177)
Balance (in units)		121,978		124,386	121,978	124,386	124,386
Distribution to Partners					$ (4,675,754)	$ (4,696,893)	$ (4,477,923)
Stock Buyback					$ (394,031)	$ (4,050,137)		$ (44,718,000)
Stock Buyback (in units)					(222)	(2,408)
Net income	$ (970,022)	$ 1,368,783	$ 1,898,513	$ 1,500,516	$ 1,424,528	$ 6,547,252	4,169,090
Balance	$ (41,469,045)		$ (37,823,788)		$ (41,469,045)	$ (37,823,788)	$ (35,624,010)	$ (41,469,045)
Balance (in units)	121,756		121,978		121,756	121,978	124,386	121,756
Subtotal
Increase (Decrease) in Partners' Capital
Balance (in units)		180,225		180,225	180,225	180,225	180,225
Balance (in units)	180,225		180,225		180,225	180,225	180,225	180,225
General Partnership
Increase (Decrease) in Partners' Capital
Balance		$ (376,827)		$ (354,833)	$ (376,827)	$ (354,833)	$ (351,745)
Balance (in units)		1,802		1,802	1,802	1,802	1,802
Distribution to Partners					$ (46,757)	$ (46,969)	$ (44,779)
Stock Buyback					$ (3,941)	$ (40,498)
Stock Buyback (in units)					(2.22)	(24.1)
Net income					$ 14,245	$ 65,473	41,691
Balance	$ (413,280)		$ (376,827)		$ (413,280)	$ (376,827)	$ (354,833)	$ (413,280)
Balance (in units)	1,802		1,802		1,802	1,802	1,802	1,802
Treasury Units
Increase (Decrease) in Partners' Capital
Balance (in units)		58,247		55,839	58,247	55,839	55,839
Stock Buyback (in units)					(222)	(2,408)
Balance (in units)	58,469		58,247		58,469	58,247	55,839	58,469
Class A
Increase (Decrease) in Partners' Capital
Balance		$ (30,287,245)		$ (28,527,352)	$ (30,287,245)	$ (28,527,352)	$ (28,280,285)
Balance (in units)		144,180		144,180	144,180	144,180	144,180
Distribution to Partners					$ (3,740,604)	$ (3,757,514)	$ (3,582,339)
Stock Buyback					(315,220)	(3,240,181)
Net income					1,139,622	5,237,802	3,335,272
Balance	$ (33,203,447)		$ (30,287,245)		$ (33,203,447)	$ (30,287,245)	$ (28,527,352)	$ (33,203,447)
Balance (in units)	144,180		144,180		144,180	144,180	144,180	144,180
Class B
Increase (Decrease) in Partners' Capital
Balance		$ (7,159,715)		$ (6,741,825)	$ (7,159,715)	$ (6,741,825)	$ (6,683,147)
Balance (in units)		34,243		34,243	34,243	34,243	34,243
Distribution to Partners					$ (888,393)	$ (892,410)	$ (850,805)
Stock Buyback					$ (74,870)	$ (769,458)
Stock Buyback (in units)					(42.18)	(457.6)
Net income					$ 270,660	$ 1,243,978	792,127
Balance	$ (7,852,318)		$ (7,159,715)		$ (7,852,318)	$ (7,159,715)	$ (6,741,825)	$ (7,852,318)
Balance (in units)	34,243		34,243		34,243	34,243	34,243	34,243