GOODWILL, TRADE NAMES, AND OTHER INTANGIBLE ASSETS - Acquired Intangible Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 88,220	$ 110,068
Accumulated Amortization	32,621	49,092
Intangible assets subject to amortization, net carrying amount	55,599	60,976
Trade names	26,702	26,702
Total intangible assets, net	82,301	87,678
Databases [Member]
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	30,384	42,909
Accumulated Amortization	8,456	18,702
Intangible assets subject to amortization, net carrying amount	21,928	24,207
Customer relationships [Member]
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	49,620	55,524
Accumulated Amortization	22,473	25,912
Intangible assets subject to amortization, net carrying amount	27,147	29,612
Non-compete agreements [Member]
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	516	3,919
Accumulated Amortization	274	3,600
Intangible assets subject to amortization, net carrying amount	242	319
Trade names [Member]
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	7,700	7,716
Accumulated Amortization	1,418	878
Intangible assets subject to amortization, net carrying amount	$ 6,282	$ 6,838