SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Other Operating items, net (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Other operating items, net	$ 1,157	$ 188	$ 2,462	$ 624
Pre-opening expenses relating to the Monarch Black Hawk Expansion project	200	$ 200	1,000	$ 600
Professional service fees relating to our construction litigation	200		300
Colorado legislation lobbing expenses	500		900
Expenses due to the COVID-19 pandemic	$ 300		$ 300