SUBSEQUENT EVENTS (Details)			1 Months Ended			3 Months Ended	12 Months Ended			137 Months Ended
	Jan. 01, 2019 USD ($) shares	Sep. 29, 2017 USD ($)	Jan. 31, 2019 USD ($)	Oct. 31, 2018 USD ($)	Jul. 31, 2018 USD ($)	Mar. 31, 2019 USD ($) $ / item shares	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($) shares	Dec. 31, 2016 USD ($) shares	Dec. 31, 2018 USD ($) $ / item shares	Feb. 24, 2019
Subsequent events
Number of depository receipts repurchased | shares								549		1,365,306
Repurchase price of depository receipts (in dollars per receipt) | $ / item										27.14
Total cost of repurchase								$ 42,548	$ 1,634,945	$ 40,274,000
Stock Buyback (in units) | shares								23	965
Payment on line of credit							$ 15,000,000	$ 24,000,000	$ 25,000,000
Line of Credit
Subsequent events
Payment on line of credit		$ 8,000,000		$ 3,000,000	$ 4,000,000
Subsequent event
Subsequent events
Number of depository receipts repurchased | shares						41,900
Repurchase price of depository receipts (in dollars per receipt) | $ / item						54.11
Price per unit of depository receipts | $ / item						1,623.00
Total cost of repurchase						$ 2,267,072
Payment on line of credit			$ 2,000,000
Percent of outstanding voting securities											75.00%
Subsequent event | President
Subsequent events
Number of depository receipts repurchased | shares						40,000
Class B
Subsequent events
Number of depository receipts repurchased | shares										3,072
Total cost of repurchase								8,084	307,436
Class B | Subsequent event
Subsequent events
Total cost of repurchase	$ 538,421
Stock Buyback (in units) | shares	332
General Partnership
Subsequent events
Number of depository receipts repurchased | shares										162
Total cost of repurchase								$ 426	$ 16,181
General Partnership | Subsequent event
Subsequent events
Total cost of repurchase	$ 28,338
Stock Buyback (in units) | shares	17