SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Promotional Allowances, Advertising Costs and Gaming Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Gaming Taxes
Gaming taxes	$ 21,600	$ 20,300	$ 18,200
Food and beverage
Promotional Allowances
Estimated departmental costs of providing promotional allowances	26,025	25,743	23,761
Hotel
Promotional Allowances
Estimated departmental costs of providing promotional allowances	3,375	3,039	3,157
Other
Promotional Allowances
Estimated departmental costs of providing promotional allowances	2,128	1,943	2,070
Promotional allowances
Promotional Allowances
Estimated departmental costs of providing promotional allowances	31,528	30,725	28,988
Selling, general and administrative
Advertising Costs
Advertising expense	$ 5,200	$ 5,400	$ 5,200