DISCONTINUED OPERATIONS - Summary of Net Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Costs and expenses:
Income from discontinued operations									$ 0	$ 18,873	$ 10,313
Gain on sale of CBR business									0	87,076	0
Income tax expense									0	2,371	4,388
Net income from discontinued operations	$ 0	$ 0	$ 0	$ 0	$ (1,531)	$ 95,517	$ 5,736	$ 3,856	$ 0	103,578	5,925
CBR business | Discontinued Operations, Held-for-sale or Disposed of by Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Service revenues, net										71,217	114,177
Costs and expenses:
Cost of services										12,559	21,817
Selling, general and administrative expenses										39,899	81,782
Total costs and expenses										52,458	103,599
Operating income										18,759	10,578
Other income (expense)										114	(265)
Income from discontinued operations										18,873	10,313
Gain on sale of CBR business										87,076	0
Income tax expense										2,371	4,388
Net income from discontinued operations										$ 103,578	$ 5,925