Supplemental Guarantors Consolidating Condensed Financial Information (Statement of Income (Loss)) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Condensed Financial Statements, Captions [Line Items]
REVENUE	$ 47,334	$ 47,544	$ 104,387	$ 98,895
EXPENSES:
Depreciation and amortization	29,771	27,829	67,629	57,167
Cost of sales	127	63	253	102
Selling, general and administrative	6,893	6,254	14,318	13,641
Total operating expenses	36,791	34,146	82,200	70,910
INCOME (LOSS) FROM OPERATIONS	10,543	13,398	22,187	27,985
Interest expense, net	(6,211)	(6,138)	(12,418)	(15,453)
Foreign currency exchange gains (losses)	831	(1,171)	(443)	(1,818)
Loss on early extinguishment of debt	0	0	0	(1,504)
Other income (loss)	73	0	59	1
Income (loss) before income taxes and equity in income (loss) of subsidiaries	5,236	6,089	9,385	9,211
Provision (benefit) for income taxes	2,661	(279)	4,918	1,105
Equity in income (loss) of subsidiaries			0	0
NET INCOME	2,575	6,368	4,467	8,106
Parent [Member]
Condensed Financial Statements, Captions [Line Items]
REVENUE			0	0
EXPENSES:
Depreciation and amortization			0	0
Cost of sales			0	0
Selling, general and administrative			607	714
Total operating expenses			607	714
INCOME (LOSS) FROM OPERATIONS			(607)	(714)
Interest expense, net			(10,589)	(12,889)
Foreign currency exchange gains (losses)			0	0
Loss on early extinguishment of debt				(1,504)
Other income (loss)			(14)
Income (loss) before income taxes and equity in income (loss) of subsidiaries			(11,210)	(15,107)
Provision (benefit) for income taxes			(4,460)	0
Equity in income (loss) of subsidiaries			11,217	23,213
NET INCOME			4,467	8,106
Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
REVENUE			76,872	76,424
EXPENSES:
Depreciation and amortization			43,560	41,352
Cost of sales			240	100
Selling, general and administrative			9,289	8,660
Total operating expenses			53,089	50,112
INCOME (LOSS) FROM OPERATIONS			23,783	26,312
Interest expense, net			(1,040)	(1,714)
Foreign currency exchange gains (losses)			3	1
Loss on early extinguishment of debt				0
Other income (loss)			73	1
Income (loss) before income taxes and equity in income (loss) of subsidiaries			22,819	24,600
Provision (benefit) for income taxes			9,841	952
Equity in income (loss) of subsidiaries			(1,791)	(435)
NET INCOME			11,187	23,213
Non-Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
REVENUE			28,205	23,124
EXPENSES:
Depreciation and amortization			24,099	15,815
Cost of sales			13	2
Selling, general and administrative			5,112	4,920
Total operating expenses			29,224	20,737
INCOME (LOSS) FROM OPERATIONS			(1,019)	2,387
Interest expense, net			(789)	(850)
Foreign currency exchange gains (losses)			(446)	(1,819)
Loss on early extinguishment of debt				0
Other income (loss)			0	0
Income (loss) before income taxes and equity in income (loss) of subsidiaries			(2,254)	(282)
Provision (benefit) for income taxes			(463)	153
Equity in income (loss) of subsidiaries			0	0
NET INCOME			(1,791)	(435)
Consolidating Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
REVENUE			(690)	(653)
EXPENSES:
Depreciation and amortization			(30)	0
Cost of sales			0	0
Selling, general and administrative			(690)	(653)
Total operating expenses			(720)	(653)
INCOME (LOSS) FROM OPERATIONS			30	0
Interest expense, net			0	0
Foreign currency exchange gains (losses)			0	0
Loss on early extinguishment of debt				0
Other income (loss)			0	0
Income (loss) before income taxes and equity in income (loss) of subsidiaries			30	0
Provision (benefit) for income taxes			0	0
Equity in income (loss) of subsidiaries			(9,426)	(22,778)
NET INCOME			$ (9,396)	$ (22,778)