QUARTERLY FINANCIAL DATA (UNAUDITED) (Details)	3 Months Ended								12 Months Ended
	Dec. 31, 2019 USD ($) $ / shares $ / item	Sep. 30, 2019 USD ($) $ / shares $ / item	Jun. 30, 2019 USD ($) $ / shares $ / item	Mar. 31, 2019 USD ($) $ / shares $ / item	Dec. 31, 2018 USD ($) $ / shares $ / item	Sep. 30, 2018 USD ($) $ / shares $ / item	Jun. 30, 2018 USD ($) $ / shares $ / item	Mar. 31, 2018 USD ($) $ / shares $ / item	Dec. 31, 2019 USD ($) $ / shares $ / item	Dec. 31, 2018 USD ($) $ / shares $ / item	Dec. 31, 2017 USD ($) $ / shares
QUARTERLY FINANCIAL DATA (UNAUDITED)
Revenue	$ 15,447,866	$ 15,155,901	$ 14,991,403	$ 14,882,144	$ 14,779,274	$ 14,545,533	$ 14,630,257	$ 14,059,000	$ 60,477,314	$ 58,014,064	$ 52,827,388
Expenses	10,883,950	10,978,884	10,412,256	10,930,457	10,710,144	11,329,228	10,759,024	10,297,296	43,205,547	43,095,692
Income Before Other Income (Expense)	4,563,916	4,177,017	4,579,147	3,951,687	4,069,130	3,216,305	3,871,233	3,761,704	17,271,767	14,918,372	14,144,966
Other Expenses	(2,665,403)	(2,793,038)	(2,814,903)	(2,451,171)	(2,492,253)	(2,555,976)	(3,817,907)	(1,883,146)	(10,724,515)	(10,749,282)	(7,207,035)
Net Income	$ 1,898,513	$ 1,383,979	$ 1,764,244	$ 1,500,516	$ 1,576,877	$ 660,329	$ 53,326	$ 1,878,558	$ 6,547,252	$ 4,169,090	$ 6,937,931
Net Income per Unit before Discontinued Operations | $ / shares	$ 15.55	$ 11.32	$ 14.40	$ 12.21	$ 12.68	$ 5.31	$ 0.43	$ 15.10	$ 53.48	$ 33.52
Net Income per Unit (in dollars per unit) | $ / shares	$ 15.55	$ 11.32	$ 14.40	$ 12.21	$ 12.68	$ 5.31	$ 0.43	$ 15.10	$ 53.48	$ 33.52	$ 55.77
Income Per Depositary Receipt Before Discontinued Operations (in dollars per unit) | $ / item	0.51	0.38	0.48	0.41	0.43	0.18	0.01	0.50	1.78	1.12
Net Income Per Depositary Receipt (in dollars per receipt) | $ / item	0.51	0.38	0.48	0.41	0.43	0.18	0.01	0.50	1.78	1.12