EMPLOYEE BENEFIT PLANS - Net Periodic Benefit (Income) (Details) - Dover Downs Pension Plan - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2019
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Interest cost	$ 666	$ 666
Expected return on plan assets		(967)
Net periodic benefit (income) cost		(301)
Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income
Net actuarial loss		2,740
Total expense recognized in other comprehensive income		2,740
Total expense recognized in net periodic benefit cost (income) and other comprehensive income (loss)		$ 2,439