GOODWILL, TRADE NAMES, AND OTHER INTANGIBLE ASSETS - Acquired Intangible Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 80,168	$ 80,168
Accumulated Amortization	45,478	43,333
Intangible assets subject to amortization, net carrying amount	34,690	36,835
Trade names	35,402	35,402
Total intangible assets, net	70,092	72,237
Database [Member]
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	31,609	31,609
Accumulated Amortization	17,162	16,147
Intangible assets subject to amortization, net carrying amount	14,447	15,462
Customer Relationships [Member]
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	41,724	41,724
Accumulated Amortization	24,270	23,316
Intangible assets subject to amortization, net carrying amount	17,454	18,408
Noncompete Agreements [Member]
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	3,619	3,619
Accumulated Amortization	3,548	3,527
Intangible assets subject to amortization, net carrying amount	71	92
Trade names [Member]
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	3,216	3,216
Accumulated Amortization	498	343
Intangible assets subject to amortization, net carrying amount	$ 2,718	$ 2,873