SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Other Operating items, net (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Other operating items, net	$ 6,711	$ 3,112	$ 12
Pre-opening expenses relating to the Monarch Black Hawk Expansion project	2,800	2,500
Professional service fees relating to our construction litigation	1,600	300
Colorado legislation lobbing expenses	1,400
Expenses due to the COVID-19 pandemic	700
Write off of Deferred Debt Issuance Cost	95
Unamortized debt issuance cost write off and loss on disposal of assets	$ 200
professional service fees relating to a due diligence on an acquisition opportunity		$ 300