GOODWILL, TRADE NAMES, AND OTHER INTANGIBLE ASSETS - Acquired Intangible Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 89,487	$ 89,487
Accumulated Amortization	36,189	34,305
Intangible assets subject to amortization, net carrying amount	53,298	55,182
Trade names	20,402	20,402
Total intangible assets, net	73,700	75,584
Databases [Member]
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	30,530	30,530
Accumulated Amortization	9,979	9,216
Intangible assets subject to amortization, net carrying amount	20,551	21,314
Customer relationships [Member]
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	49,758	49,758
Accumulated Amortization	24,121	23,296
Intangible assets subject to amortization, net carrying amount	25,637	26,462
Non-compete agreements [Member]
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	320	320
Accumulated Amortization	113	97
Intangible assets subject to amortization, net carrying amount	207	223
Trade names [Member]
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	8,879	8,879
Accumulated Amortization	1,976	1,696
Intangible assets subject to amortization, net carrying amount	$ 6,903	$ 7,183