CONSOLIDATED STATEMENTS OF CHANGES IN PARTNER'S CAPITAL - USD ($)	3 Months Ended				12 Months Ended			149 Months Ended
	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2019
Increase (Decrease) in Partners' Capital
Balance		$ (35,624,010)		$ (35,315,177)	$ (35,624,010)	$ (35,315,177)	$ (34,224,725)
Balance (in units)		124,386		124,386	124,386	124,386	124,409
Distribution to Partners					$ (4,696,893)	$ (4,477,923)	$ (7,985,835)
Stock Buyback					$ (4,050,137)		$ (42,548)	$ (44,324,000)
Stock Buyback (in units)					(2,408)		(23)
Net income	$ 1,898,513	$ 1,500,516	$ 1,576,877	$ 1,878,558	$ 6,547,252	4,169,090	$ 6,937,931
Balance	$ (37,823,788)		$ (35,624,010)		$ (37,823,788)	$ (35,624,010)	$ (35,315,177)	$ (37,823,788)
Balance (in units)	121,978		124,386		121,978	124,386	124,386	121,978
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		$ (354,833)		$ (351,745)	$ (354,833)	$ (351,745)	$ (340,840)
Balance (in units)		1,802		1,802	1,802	1,802	1,802
Distribution to Partners					$ (46,969)	$ (44,779)	$ (79,858)
Stock Buyback					(40,498)	(40,498)	(426)
Net income					65,473	41,691	69,379
Balance	$ (376,827)		$ (354,833)		$ (376,827)	$ (354,833)	$ (351,745)	$ (376,827)
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)		55,839		55,839	55,839	55,839	55,816
Stock Buyback (in units)					(2,408)		(23)
Balance (in units)	58,247		55,839		58,247	55,839	55,839	58,247
Class A
Increase (Decrease) in Partners' Capital
Balance		$ (28,527,352)		$ (28,280,285)	$ (28,527,352)	$ (28,280,285)	$ (27,407,924)
Balance (in units)		144,180		144,180	144,180	144,180	144,180
Distribution to Partners					$ (3,757,514)	$ (3,582,339)	$ (6,388,668)
Stock Buyback					(3,240,181)		(34,038)
Net income					5,237,802	3,335,272	5,550,345
Balance	$ (30,287,245)		$ (28,527,352)		$ (30,287,245)	$ (28,527,352)	$ (28,280,285)	$ (30,287,245)
Balance (in units)	144,180		144,180		144,180	144,180	144,180	144,180
Class B
Increase (Decrease) in Partners' Capital
Balance		$ (6,741,825)		$ (6,683,147)	$ (6,741,825)	$ (6,683,147)	$ (6,475,961)
Balance (in units)		34,243		34,243	34,243	34,243	34,243
Distribution to Partners					$ (892,410)	$ (850,805)	$ (1,517,309)
Stock Buyback					(769,458)		(8,084)
Net income					1,243,978	792,127	1,318,207
Balance	$ (7,159,715)		$ (6,741,825)		$ (7,159,715)	$ (6,741,825)	$ (6,683,147)	$ (7,159,715)
Balance (in units)	34,243		34,243		34,243	34,243	34,243	34,243