GOODWILL, TRADE NAMES, AND OTHER INTANGIBLE ASSETS - Acquired Intangible Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 110,068	$ 110,068
Accumulated Amortization	50,883	49,092
Intangible assets subject to amortization, net carrying amount	59,185	60,976
Trade names	26,702	26,702
Total intangible assets, net	85,887	87,678
Databases [Member]
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	42,909	42,909
Accumulated Amortization	19,461	18,702
Intangible assets subject to amortization, net carrying amount	23,448	24,207
Customer relationships [Member]
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	55,524	55,524
Accumulated Amortization	26,734	25,912
Intangible assets subject to amortization, net carrying amount	28,790	29,612
Non-compete agreements [Member]
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	3,919	3,919
Accumulated Amortization	3,626	3,600
Intangible assets subject to amortization, net carrying amount	293	319
Trade names [Member]
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	7,716	7,716
Accumulated Amortization	1,062	878
Intangible assets subject to amortization, net carrying amount	$ 6,654	$ 6,838