EQUITY STRUCTURE AND ACCOUNTS - Schedule of repurchase of treasury stock activity (Details) - 2014 Share Repurchase Authorization Program - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018	Oct. 30, 2014
Treasury Stock [Roll Forward]
Remaining amount available for repurchase	$ 41,800
Class A Common Stock
Class of Stock [Line Items]
Purchase of treasury stock (in shares)	0	0
Treasury Stock [Roll Forward]
Remaining amount available for repurchase	$ 41,769	$ 41,769
Additional authorizations	0	0	$ 50,000
Repurchases paid	0	0
Repurchases unsettled	0	0
Remaining amount available for repurchase	$ 41,769	$ 41,769

Equity impact of the cost of common and preferred stock that were repurchased during the period. Recorded using the cost method.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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Balance Type:	debit
Period Type:	duration