SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Adjustments to Previously Issued Quarterly Financial Statements (Details) - USD ($) $ in Thousands	3 Months Ended												6 Months Ended			9 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, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2017	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net revenues	$ 71,650	$ 72,960	$ 73,022	$ 73,873	$ 77,155	$ 82,928	$ 82,253	$ 73,822					$ 146,668	$ 156,075		$ 219,628	$ 239,003		$ 291,505	$ 316,158	$ 280,718
Costs of sales and services, exclusive of depreciation and amortization	27,703	27,549	26,045	25,649	27,022	28,212	27,638	24,777					51,694	52,415		79,243	80,628		106,946	107,649	106,217
Sales, general and administrative			15,312	18,225	17,648	17,985	19,591	19,801					33,204	39,392			57,376		67,050	75,023	62,728
Depreciation and amortization		20,999	21,505	22,176	22,710	23,009	22,179	20,523	$ 16,793	$ 20,320	$ 18,755	$ 17,561	43,321	42,702	$ 36,316	64,320	65,710	$ 56,636	85,713	88,416	73,429
Exit activities, restructuring and impairments		4,918														6,565			8,986	5,406	6,249
Interest expense		19,620	19,258	17,501	18,049	17,849	16,790	15,133	13,213	12,648	16,935		36,759	31,923	25,072	56,379	49,773	37,720	75,142	67,823	50,933
Net loss attributable to shareholders		(24,083)	(17,982)	(20,007)	(18,880)	(14,840)	(13,802)	(13,678)	(6,649)	(10,647)	(18,894)	(8,046)	(37,989)	(27,480)	(26,940)	(62,072)	(42,320)	(37,587)	(138,250)	(61,200)	(44,236)
Cash and cash equivalents	11,649				17,823				14,041										11,649	17,823	14,041
Accounts receivable, net	15,567	17,244	17,859		19,623	22,867	20,163	17,145	18,356				17,859	20,163		17,244	22,867		15,567	19,623	18,356
Contract assets - current	9,039				8,844			7,497											9,039	8,844
Prepaid expenses and other assets	7,370				7,377					9,615								9,615	7,370	7,377
Property and equipment, net	215,111	220,645	228,210	233,391	484,306	493,315	468,428	476,439	460,634	442,704	428,741	292,272	228,210	468,428	428,741	220,645	493,315	442,704	215,111	484,306	460,634
Finance lease right-of-use assets	141,323	226,423	231,123	238,119									231,123			226,423			141,323
Goodwill	71,208				116,217		740,089	117,097	50,209					740,089					71,208	116,217	50,209
Contract assets - noncurrent	14,827				16,104			12,126											14,827	16,104
Total assets	599,354	727,898	746,700	754,590	750,745	761,798	16,893	746,122	588,594	569,476	561,936	415,797	746,700	16,893	561,936	727,898	761,798	569,476	599,354	750,745	588,594
Accrued liabilities	10,721				15,207	17,617		14,196	16,226								17,617		10,721	15,207	16,226
Deferred revenues - current	6,576	7,422	7,846	8,320	8,462			6,531					7,846			7,422			6,576	8,462
Short-term finance lease liabilities	4,979	5,879	6,111	8,421									6,111			5,879			4,979
Deferred revenues - noncurrent	632	561	696	808	856								696			561			632	856
Finance lease liabilities	170,042	264,265	264,765	264,959									264,765			264,265			170,042
Accounts payable	20,529				23,435					17,311								17,311	20,529	23,435
Capital lease obligations - current	0				9,171	9,485	10,255	10,028	10,266	10,284				10,255			9,485	10,284	0	9,171	10,266
Other long-term liabilities	3,622				3,473			3,847											3,622	3,473
Capital lease obligations - noncurrent					264,741	266,067	233,996	236,497	225,543	208,721				233,996			266,067	208,721		264,741	225,543
Term loan, less discount and issuance costs	0				415,278				287,635	287,824	288,044				288,044			287,824	0	415,278	287,635
Total liabilities	732,176	785,198	781,112	771,640	747,776	778,382	742,846	737,357	588,014	563,750	550,351		781,112	742,846	550,351	785,198	778,382	563,750	732,176	747,776	588,014
Additional paid-in capital	1,374,230			1,370,186	1,368,968		1,329,266							1,329,266					1,374,230	1,368,968
Accumulated deficit	(1,498,409)	(1,422,231)	(1,398,148)	(1,380,166)	(1,360,107)	(1,341,228)	(1,326,387)	(1,310,609)	(1,322,111)	(1,315,462)	(1,304,816)	(1,285,890)	(1,398,148)	(1,326,387)	(1,304,816)	(1,422,231)	(1,341,228)	(1,315,462)	(1,498,409)	(1,360,107)	(1,322,111)
Total stockholders' equity (deficit)	$ (132,822)	(57,303)	(34,411)	(17,423)	2,969	(16,585)	(3,008)	11,811	580	5,936	11,585	29,991	(34,411)	(3,008)	11,585	(57,303)	(16,585)	5,936	$ (132,822)	2,969	580	$ (3,724)
As reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net revenues		72,878	73,134	73,564	78,238	82,972	81,962	74,201					146,698	156,163		219,576	239,135			317,373
Costs of sales and services, exclusive of depreciation and amortization		27,504	25,949	25,733	27,102	28,221	27,331	24,607					51,682	51,938		79,186	80,160			107,262
Sales, general and administrative			15,683	17,521	17,731	18,170	19,602	19,854					33,204	39,456			57,625			75,356
Depreciation and amortization		21,582	21,955	22,178	23,254	23,553	22,712	21,158	17,397	20,917	18,934	17,745	44,133	43,870	36,679	65,715	67,422	57,596		90,676	74,993
Exit activities, restructuring and impairments		3,792														5,439
Interest expense		19,913	19,218	17,447	17,994	17,794	16,739	15,604	12,895	12,299	17,145		36,665	32,343	25,282	56,578	50,138	37,581		68,132	50,476
Net loss attributable to shareholders		(23,870)	(18,555)	(19,644)	(18,454)	(15,479)	(14,279)	(14,288)	(6,934)	(10,895)	(19,283)	(8,230)	(38,199)	(28,567)	(27,513)	(62,069)	(44,046)	(38,409)		(62,500)	(45,343)
Cash and cash equivalents									14,603												14,603
Accounts receivable, net		17,948	18,563		20,054	22,999	20,251	17,524	17,794				18,563	20,251		17,948	22,999			20,054	17,794
Contract assets - current								7,131
Prepaid expenses and other assets										9,036								9,036
Property and equipment, net		216,548	223,497	229,185	478,061	487,616	463,273	471,752	458,565	441,239	427,873	291,583	223,497	463,273	427,873	216,548	487,616	441,239		478,061	458,565
Finance lease right-of-use assets		226,619	229,228	236,077									229,228			226,619
Goodwill							735,022	118,077						735,022
Contract assets - noncurrent								12,056
Total assets		724,701	740,796	748,342	744,931	756,231	17,059	742,358	586,525	567,432	561,068	415,108	740,796	17,059	561,068	724,701	756,231	567,432		744,931	586,525
Accrued liabilities					15,540	17,866		14,279	15,908								17,866			15,540	15,908
Deferred revenues - current		7,493	7,917	7,881	8,022			5,871					7,917			7,493				8,022
Short-term finance lease liabilities		5,867	5,930	8,328									5,930			5,867
Deferred revenues - noncurrent		259	312	341	511								312			259				511
Finance lease liabilities		264,223	262,476	262,632									262,476			264,223
Accounts payable										16,732								16,732
Capital lease obligations - current					9,080	9,399	10,246	10,095	11,711	11,729				10,246			9,399	11,729		9,080	11,711
Other long-term liabilities								3,046
Capital lease obligations - noncurrent					262,382	263,676	231,576	234,199	223,749	206,927				231,576			263,676	206,927		262,382	223,749
Term loan, less discount and issuance costs									287,845	288,034	288,254				288,254			288,034			287,845
Total liabilities		784,913	778,329	768,314	744,874	776,154	740,583	733,748	587,557	562,822	550,561		778,329	740,583	550,561	784,913	776,154	562,822		744,874	587,557
Additional paid-in capital				1,369,815			1,329,368							1,329,368
Accumulated deficit		(1,425,140)	(1,401,270)	(1,382,715)	(1,363,019)	(1,344,566)	(1,329,086)	(1,313,826)	(1,323,723)	(1,316,788)	(1,305,894)	(1,286,579)	(1,401,270)	(1,329,086)	(1,305,894)	(1,425,140)	(1,344,566)	(1,316,788)		(1,363,019)	(1,323,723)
Total stockholders' equity (deficit)		(60,212)	(37,533)	(19,972)	57	(19,923)	(5,605)	8,594	(1,032)	4,610	10,507	29,302	(37,533)	(5,605)	10,507	(60,212)	(19,923)	4,610		57	(1,032)
Adjustments | Adjustment
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net revenues		82	(112)	309	(1,083)	(44)	291	(379)					(30)	(88)		52	(132)			(1,215)
Costs of sales and services, exclusive of depreciation and amortization		45	96	(84)	(80)	(9)	307	170					12	477		57	468			387
Sales, general and administrative			(371)	704	(83)	(185)	(11)	(53)					0	(64)			(249)			(333)
Depreciation and amortization		(583)	(450)	(2)	(544)	(544)	(533)	(635)	(604)	(597)	(179)	(184)	(812)	(1,168)	(363)	(1,395)	(1,712)	(960)		(2,260)	(1,564)
Exit activities, restructuring and impairments		1,126														1,126
Interest expense		(293)	40	54	55	55	51	(471)	318	349	(210)		94	(420)	(210)	(199)	(365)	139		(309)	457
Net loss attributable to shareholders		(213)	573	(363)	(426)	639	477	610	285	248	389	184	210	1,087	573	(3)	1,726	822		1,300	1,107
Cash and cash equivalents									(562)												(562)
Accounts receivable, net		(704)	(704)		(431)	(132)	(88)	(379)	562				(704)	(88)		(704)	(132)			(431)	562
Contract assets - current								366
Prepaid expenses and other assets										579								579
Property and equipment, net		4,097	4,713	4,206	6,245	5,699	5,155	4,687	2,069	1,465	868	689	4,713	5,155	868	4,097	5,699	1,465		6,245	2,069
Finance lease right-of-use assets		(196)	1,895	2,042									1,895			(196)
Goodwill							5,067	(980)						5,067
Contract assets - noncurrent								70
Total assets		3,197	5,904	6,248	5,814	5,567	(166)	3,764	2,069	2,044	868	689	5,904	(166)	868	3,197	5,567	2,044		5,814	2,069
Accrued liabilities					(333)	(249)		(83)	318								(249)			(333)	318
Deferred revenues - current		(71)	(71)	439	440			660					(71)			(71)				440
Short-term finance lease liabilities		12	181	93									181			12
Deferred revenues - noncurrent		302	384	467	345								384			302				345
Finance lease liabilities		42	2,289	2,327									2,289			42
Accounts payable										579								579
Capital lease obligations - current					91	86	9	(67)	(1,445)	(1,445)				9			86	(1,445)		91	(1,445)
Other long-term liabilities								801
Capital lease obligations - noncurrent					2,359	2,391	2,420	2,298	1,794	1,794				2,420			2,391	1,794		2,359	1,794
Term loan, less discount and issuance costs									(210)	(210)	(210)				(210)			(210)			(210)
Total liabilities		285	2,783	3,326	2,902	2,228	2,263	3,609	457	928	(210)		2,783	2,263	(210)	285	2,228	928		2,902	457
Additional paid-in capital				371			(102)							(102)
Accumulated deficit		2,909	3,122	2,549	2,912	3,338	2,699	3,217	1,612	1,326	1,078	689	3,122	2,699	1,078	2,909	3,338	1,326		2,912	1,612
Total stockholders' equity (deficit)		$ 2,909	$ 3,122	$ 2,549	$ 2,912	$ 3,338	$ 2,597	$ 3,217	$ 1,612	$ 1,326	$ 1,078	$ 689	$ 3,122	$ 2,597	$ 1,078	$ 2,909	$ 3,338	$ 1,326		$ 2,912	$ 1,612