CONDENSED CONSOLIDATING FINANCIAL INFORMATION - Operations (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
CONDENSED CONSOLIDATING FINANCIAL INFORMATION
Net revenues	$ 325,176		$ 333,532		$ 650,838	$ 672,181
Operating expenses:
Cost of services and products (exclusive of depreciation and amortization)	139,534		143,780		277,289	292,099
Selling, general and administrative expenses	64,796		78,148		132,613	152,515
Depreciation and amortization	81,066		97,304		163,804	196,547
Income from operations	39,780		14,300		77,132	31,020
Other income (expense):
Interest expense, net of interest income	(31,459)		(34,737)		(63,554)	(69,020)
Gain on extinguishment of debt			249		234	249
Investment income	9,180		10,750		19,759	19,351
Other, net	709		(1,652)		5,303	(3,021)
Income (loss) before income taxes	18,210		(11,090)		38,874	(21,421)
Income tax expense (benefit)	4,275		(3,778)		9,316	(6,923)
Net income (loss)	13,935	$ 15,623	(7,312)	$ (7,186)	29,558	(14,498)
Less: net income (loss) attributable to noncontrolling interest	95		75		171	154
Net income (loss) attributable to common shareholders	13,840		(7,387)		29,387	(14,652)
Total comprehensive income (loss) attributable to common shareholders	16,289		(18,947)		21,836	(32,658)
Eliminations
CONDENSED CONSOLIDATING FINANCIAL INFORMATION
Net revenues	(3,091)		(3,160)		(6,145)	(6,258)
Operating expenses:
Cost of services and products (exclusive of depreciation and amortization)	(2,982)		(3,044)		(5,930)	(6,032)
Selling, general and administrative expenses	(109)		(116)		(215)	(226)
Other income (expense):
Equity in earnings of subsidiaries, net	(44,277)		(1,392)		(89,636)	(2,771)
Income (loss) before income taxes	(44,277)		(1,392)		(89,636)	(2,771)
Net income (loss)	(44,277)		(1,392)		(89,636)	(2,771)
Net income (loss) attributable to common shareholders	(44,277)		(1,392)		(89,636)	(2,771)
Total comprehensive income (loss) attributable to common shareholders	(47,061)		9,142		(82,756)	13,183
Parent | Reportable legal entity
Operating expenses:
Selling, general and administrative expenses	2,521		2,012		3,599	3,667
Income from operations	(2,521)		(2,012)		(3,599)	(3,667)
Other income (expense):
Interest expense, net of interest income	(25)		(27)		(50)	(55)
Equity in earnings of subsidiaries, net	15,779		(6,015)		32,162	(12,091)
Other, net			4			1
Income (loss) before income taxes	13,233		(8,050)		28,513	(15,812)
Income tax expense (benefit)	(607)		(663)		(874)	(1,160)
Net income (loss)	13,840		(7,387)		29,387	(14,652)
Net income (loss) attributable to common shareholders	13,840		(7,387)		29,387	(14,652)
Total comprehensive income (loss) attributable to common shareholders	16,289		(18,947)		21,836	(32,658)
Subsidiary Issuer | Reportable legal entity
Operating expenses:
Selling, general and administrative expenses	1				1	(193)
Income from operations	(1)				(1)	193
Other income (expense):
Interest expense, net of interest income	(31,035)		(34,628)		(62,589)	(68,716)
Intercompany interest income (expense)	14,727		14,727		29,454	29,454
Gain on extinguishment of debt			249		234	249
Investment income					202	190
Equity in earnings of subsidiaries, net	28,238		7,202		57,007	14,444
Other, net			(14)			42
Income (loss) before income taxes	11,929		(12,464)		24,307	(24,144)
Income tax expense (benefit)	(3,850)		(6,449)		(7,855)	(12,053)
Net income (loss)	15,779		(6,015)		32,162	(12,091)
Net income (loss) attributable to common shareholders	15,779		(6,015)		32,162	(12,091)
Total comprehensive income (loss) attributable to common shareholders	18,228		(17,575)		24,611	(30,097)
Guarantors | Reportable legal entity
CONDENSED CONSOLIDATING FINANCIAL INFORMATION
Net revenues	316,557		324,710		633,611	653,988
Operating expenses:
Cost of services and products (exclusive of depreciation and amortization)	138,779		143,283		275,813	291,084
Selling, general and administrative expenses	60,561		73,707		125,407	144,307
Depreciation and amortization	78,568		94,811		158,826	191,592
Income from operations	38,649		12,909		73,565	27,005
Other income (expense):
Interest expense, net of interest income	(425)		(90)		(951)	(257)
Intercompany interest income (expense)	(14,711)		(14,707)		(29,422)	(29,415)
Investment income	9,180		10,750		19,557	19,161
Equity in earnings of subsidiaries, net	260		205		467	418
Other, net	653		(1,625)		5,191	(3,033)
Income (loss) before income taxes	33,606		7,442		68,407	13,879
Income tax expense (benefit)	7,854		2,215		16,296	3,971
Net income (loss)	25,752		5,227		52,111	9,908
Less: net income (loss) attributable to noncontrolling interest	95		75		171	154
Net income (loss) attributable to common shareholders	25,657		5,152		51,940	9,754
Total comprehensive income (loss) attributable to common shareholders	25,983		6,110		52,593	11,670
Non-Guarantors | Reportable legal entity
CONDENSED CONSOLIDATING FINANCIAL INFORMATION
Net revenues	11,710		11,982		23,372	24,451
Operating expenses:
Cost of services and products (exclusive of depreciation and amortization)	3,737		3,541		7,406	7,047
Selling, general and administrative expenses	1,822		2,545		3,821	4,960
Depreciation and amortization	2,498		2,493		4,978	4,955
Income from operations	3,653		3,403		7,167	7,489
Other income (expense):
Interest expense, net of interest income	26		8		36	8
Intercompany interest income (expense)	(16)		(20)		(32)	(39)
Other, net	56		(17)		112	(31)
Income (loss) before income taxes	3,719		3,374		7,283	7,427
Income tax expense (benefit)	878		1,119		1,749	2,319
Net income (loss)	2,841		2,255		5,534	5,108
Net income (loss) attributable to common shareholders	2,841		2,255		5,534	5,108
Total comprehensive income (loss) attributable to common shareholders	$ 2,850		$ 2,323		$ 5,552	$ 5,244