Supplemental Guarantors Consolidating Condensed Financial Information (Statement of Operations) (Details) (USD $)
In Thousands, unless otherwise specified
 3 Months Ended 6 Months Ended
Jun. 30, 2012
Jun. 30, 2011
Jun. 30, 2012
Jun. 30, 2011
Condensed Financial Statements, Captions [Line Items]        
REVENUE $ 46,028 $ 35,545 $ 118,575 $ 95,041
EXPENSES:        
Depreciation and amortization 29,837 23,246 69,221 65,660
Cost of sales 151 39 248 55
Selling, general and administrative 7,705 7,925 15,797 15,490
Total operating expenses 37,693 31,210 85,266 81,205
INCOME (LOSS) FROM OPERATIONS 8,335 4,335 33,309 13,836
Interest expense, net (7,253) (10,265) (14,472) (20,424)
Foreign currency exchange losses (426) 225 (15) 457
Gain on sale of marketable securities 230 980 230 2,467
Other income 402 115 483 164
Income (loss) before income taxes and equity in income of subsidiaries 1,288 (4,610) 19,535 (3,500)
Provision for income taxes 18 416 3,559 1,015
Equity in income of subsidiaries     0 0
NET INCOME (LOSS) 1,270 (5,026) 15,976 (4,515)
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     1,174 1,042
Total operating expenses     1,174 1,042
INCOME (LOSS) FROM OPERATIONS     (1,174) (1,042)
Interest expense, net     (5,374) (10,146)
Foreign currency exchange losses     0 0
Gain on sale of marketable securities     0 0
Other income     1 2
Income (loss) before income taxes and equity in income of subsidiaries     (6,547) (11,186)
Provision for income taxes     0 0
Equity in income of subsidiaries     22,523 6,671
NET INCOME (LOSS)     15,976 (4,515)
Guarantor Subsidiaries [Member]
        
Condensed Financial Statements, Captions [Line Items]        
REVENUE     70,421 66,412
EXPENSES:        
Depreciation and amortization     40,248 42,731
Cost of sales     235 51
Selling, general and administrative     9,306 9,437
Total operating expenses     49,789 52,219
INCOME (LOSS) FROM OPERATIONS     20,632 14,193
Interest expense, net     (8,464) (9,936)
Foreign currency exchange losses     (4) 4
Gain on sale of marketable securities     230 2,467
Other income     482 27
Income (loss) before income taxes and equity in income of subsidiaries     12,876 6,755
Provision for income taxes     88 438
Equity in income of subsidiaries     9,735 354
NET INCOME (LOSS)     22,523 6,671
Non-Guarantor Subsidiaries [Member]
        
Condensed Financial Statements, Captions [Line Items]        
REVENUE     48,836 29,264
EXPENSES:        
Depreciation and amortization     28,973 22,929
Cost of sales     13 4
Selling, general and administrative     5,999 5,646
Total operating expenses     34,985 28,579
INCOME (LOSS) FROM OPERATIONS     13,851 685
Interest expense, net     (634) (342)
Foreign currency exchange losses     (11) 453
Gain on sale of marketable securities     0 0
Other income     0 135
Income (loss) before income taxes and equity in income of subsidiaries     13,206 931
Provision for income taxes     3,471 577
Equity in income of subsidiaries     0 0
NET INCOME (LOSS)     9,735 354
Consolidating Eliminations [Member]
        
Condensed Financial Statements, Captions [Line Items]        
REVENUE     (682) (635)
EXPENSES:        
Depreciation and amortization     0 0
Cost of sales     0 0
Selling, general and administrative     (682) (635)
Total operating expenses     (682) (635)
INCOME (LOSS) FROM OPERATIONS     0 0
Interest expense, net     0 0
Foreign currency exchange losses     0 0
Gain on sale of marketable securities     0 0
Other income     0 0
Income (loss) before income taxes and equity in income of subsidiaries     0 0
Provision for income taxes     0 0
Equity in income of subsidiaries     (32,258) (7,025)
NET INCOME (LOSS)     $ (32,258) $ (7,025)