SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Other Operating items, net (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Other operating items, net	$ 2,448	$ 1,115	$ 4,910	$ 1,739
Pre-opening expenses relating to the Monarch Black Hawk Expansion project	900	900	1,900	1,500
Professional service fees relating to our construction litigation	500	$ 200	800	$ 200
Colorado legislation lobbing expenses	500		1,400
Expenses due to the COVID-19 pandemic	400		700
Write off of Deferred Debt Issuance Cost	$ 100		$ 95