EQUITY STRUCTURE AND ACCOUNTS - Schedule of repurchase of treasury stock activity (Details) - USD ($)	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019	Jun. 30, 2018	Oct. 30, 2014
Treasury Stock [Roll Forward]
Repurchases paid	$ (637,000)	$ (637,000)
2014 Share Repurchase Authorization Program
Treasury Stock [Roll Forward]
Remaining amount available for repurchase	41,100,000	$ 41,100,000
2014 Share Repurchase Authorization Program | Class A Common Stock
Class of Stock [Line Items]
Purchase of treasury stock (in shares)		40,065	40,065
Treasury Stock [Roll Forward]
Remaining amount available for repurchase		$ 41,769,000	$ 41,769,000
Additional authorizations	0	0	0	$ 50,000,000.0
Repurchases paid		(637,000)	0
Repurchases unsettled		0	0
Remaining amount available for repurchase	$ 41,132,000	$ 41,132,000	$ 41,769,000