Supplemental Guarantors Consolidating Condensed Financial Information - (Statement of Operations) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Condensed Financial Statements, Captions [Line Items]
REVENUE	$ 52,351	$ 41,299	$ 47,334	$ 57,053	$ 59,569	$ 44,410	$ 47,544	$ 51,351	$ 198,037	$ 202,874	$ 240,458
EXPENSES:
Depreciation and amortization									121,023	121,598	139,754
Cost of sales									304	475	464
Selling, general and administrative									29,799	25,971	29,088
Total operating expenses									151,126	148,044	169,306
INCOME (LOSS) FROM OPERATIONS	8,944	15,780	10,543	11,644	20,620	6,225	13,398	14,587	46,911	54,830	71,152
Interest expense, net									(25,029)	(27,851)	(29,011)
Foreign currency exchange gains (losses)									(1,974)	(2,222)	681
Gain on sale of marketable securities									0	0	230
Loss on early extinguishment of debt									0	(1,504)	0
Other income									63	488	780
Income before income taxes									19,971	23,741	43,832
Provision (benefit) for income taxes									10,293	(89,940)	6,782
Equity in income of subsidiaries									0	0	0
NET INCOME	725	4,486	2,575	1,892	105,338	237	6,368	1,738	9,678	113,681	37,050
Parent [Member]
Condensed Financial Statements, Captions [Line Items]
REVENUE									0	0	0
EXPENSES:
Depreciation and amortization									0	0	0
Cost of sales									0	0	0
Selling, general and administrative									2,130	1,587	2,117
Total operating expenses									2,130	1,587	2,117
INCOME (LOSS) FROM OPERATIONS									(2,130)	(1,587)	(2,117)
Interest expense, net									(21,407)	(23,194)	(21,542)
Foreign currency exchange gains (losses)									0	0	0
Gain on sale of marketable securities											0
Loss on early extinguishment of debt										(1,504)
Other income									(14)	0	21
Income before income taxes									(23,551)	(26,285)	(23,638)
Provision (benefit) for income taxes									(9,270)	0	0
Equity in income of subsidiaries									23,959	139,966	60,688
NET INCOME									9,678	113,681	37,050
Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
REVENUE									153,125	154,686	157,324
EXPENSES:
Depreciation and amortization									80,835	86,426	88,724
Cost of sales									284	471	446
Selling, general and administrative									19,304	16,701	17,607
Total operating expenses									100,423	103,598	106,777
INCOME (LOSS) FROM OPERATIONS									52,702	51,088	50,547
Interest expense, net									(2,360)	(2,945)	(6,015)
Foreign currency exchange gains (losses)									3	0	(4)
Gain on sale of marketable securities											230
Loss on early extinguishment of debt										0
Other income									71	737	759
Income before income taxes									50,416	48,880	45,517
Provision (benefit) for income taxes									21,063	(90,320)	1,377
Equity in income of subsidiaries									(5,452)	984	16,548
NET INCOME									23,901	140,184	60,688
Non-Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
REVENUE									46,287	49,488	84,435
EXPENSES:
Depreciation and amortization									40,246	35,203	51,030
Cost of sales									20	4	18
Selling, general and administrative									9,740	8,983	10,665
Total operating expenses									50,006	44,190	61,713
INCOME (LOSS) FROM OPERATIONS									(3,719)	5,298	22,722
Interest expense, net									(1,262)	(1,712)	(1,454)
Foreign currency exchange gains (losses)									(1,977)	(2,222)	685
Gain on sale of marketable securities											0
Loss on early extinguishment of debt										0
Other income									6	0	0
Income before income taxes									(6,952)	1,364	21,953
Provision (benefit) for income taxes									(1,500)	380	5,405
Equity in income of subsidiaries									0	0	0
NET INCOME									(5,452)	984	16,548
Consolidating Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
REVENUE									(1,375)	(1,300)	(1,301)
EXPENSES:
Depreciation and amortization									(58)	(31)	0
Cost of sales									0	0	0
Selling, general and administrative									(1,375)	(1,300)	(1,301)
Total operating expenses									(1,433)	(1,331)	(1,301)
INCOME (LOSS) FROM OPERATIONS									58	31	0
Interest expense, net									0	0	0
Foreign currency exchange gains (losses)									0	0	0
Gain on sale of marketable securities											0
Loss on early extinguishment of debt										0
Other income									0	(249)	0
Income before income taxes									58	(218)	0
Provision (benefit) for income taxes									0	0	0
Equity in income of subsidiaries									(18,507)	(140,950)	(77,236)
NET INCOME									$ (18,449)	$ (141,168)	$ (77,236)