Guarantor/Non Guarantor Condensed Consolidated Financial Statements (Balance Sheet (Unaudited)) (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 18,669	$ 14,160	$ 35,678	$ 34,924
Receivables, net of allowance	65,423	79,816
Intercompany receivable (payable)	0	0
Inventory	8,501	9,262
Assets held for sale	4,276	4,619
Prepaid expenses and other current assets	6,678	7,411
Total current assets	103,547	115,268
Net property and equipment	679,268	702,585
Investments in subsidiaries	0	0
Intangible assets, net of accumulated amortization	1,551	1,944
Deferred income taxes	22	18
Other long-term assets	2,137	2,178
Total assets	786,525	821,993	1,123,850
Current liabilities:
Accounts payable	12,966	16,951
Deferred revenues	7,878	6,222
Accrued expenses	41,596	46,869
Total current liabilities	62,440	70,042
Long-term debt, less current portion	387,621	387,217
Deferred income taxes	16,288	17,520
Other long-term liabilities	5,064	4,571
Total liabilities	471,413	479,350
Total shareholders' equity	315,112	342,643
Total liabilities and shareholders' equity	786,525	821,993
Guarantor Subsidiaries [Member]
Current assets:
Cash and cash equivalents	152	(5,612)	(2,789)	(5,516)
Receivables, net of allowance	56,590	67,174
Intercompany receivable (payable)	31,628	31,108
Inventory	4,854	5,591
Assets held for sale	4,276	4,619
Prepaid expenses and other current assets	4,038	4,767
Total current assets	101,538	107,647
Net property and equipment	645,879	667,321
Investments in subsidiaries	37,358	42,240
Intangible assets, net of accumulated amortization	1,551	1,944
Deferred income taxes	0	0
Other long-term assets	893	962
Total assets	787,219	820,114
Current liabilities:
Accounts payable	11,693	14,628
Deferred revenues	7,350	5,570
Accrued expenses	35,754	37,023
Total current liabilities	54,797	57,221
Long-term debt, less current portion	0	0
Deferred income taxes	102,209	102,509
Other long-term liabilities	3,514	3,294
Total liabilities	160,520	163,024
Total shareholders' equity	626,699	657,090
Total liabilities and shareholders' equity	787,219	820,114
Non-Guarantor Subsidiaries [Member]
Current assets:
Cash and cash equivalents	2,735	2,551	8,949	12,752
Receivables, net of allowance	8,817	12,568
Intercompany receivable (payable)	(6,792)	(6,272)
Inventory	3,647	3,671
Assets held for sale	0	0
Prepaid expenses and other current assets	1,551	1,444
Total current assets	9,958	13,962
Net property and equipment	30,314	31,953
Investments in subsidiaries	0	0
Intangible assets, net of accumulated amortization	0	0
Deferred income taxes	22	18
Other long-term assets	852	704
Total assets	41,146	46,637
Current liabilities:
Accounts payable	757	1,707
Deferred revenues	528	652
Accrued expenses	1,994	1,473
Total current liabilities	3,279	3,832
Long-term debt, less current portion	0	0
Deferred income taxes	0	0
Other long-term liabilities	509	565
Total liabilities	3,788	4,397
Total shareholders' equity	37,358	42,240
Total liabilities and shareholders' equity	41,146	46,637
Eliminations [Member]
Current assets:
Cash and cash equivalents	0	0
Receivables, net of allowance	0	0
Intercompany receivable (payable)	0	0
Inventory	0	0
Assets held for sale	0	0
Prepaid expenses and other current assets	0	0
Total current assets	0	0
Net property and equipment	0	0
Investments in subsidiaries	(664,057)	(699,330)
Intangible assets, net of accumulated amortization	0	0
Deferred income taxes	(85,921)	(84,989)
Other long-term assets	0	0
Total assets	(749,978)	(784,319)
Current liabilities:
Accounts payable	0	0
Deferred revenues	0	0
Accrued expenses	0	0
Total current liabilities	0	0
Long-term debt, less current portion	0	0
Deferred income taxes	(85,921)	(84,989)
Other long-term liabilities	0	0
Total liabilities	(85,921)	(84,989)
Total shareholders' equity	(664,057)	(699,330)
Total liabilities and shareholders' equity	(749,978)	(784,319)
Parent [Member]
Current assets:
Cash and cash equivalents	15,782	17,221	$ 29,518	$ 27,688
Receivables, net of allowance	16	74
Intercompany receivable (payable)	(24,836)	(24,836)
Inventory	0	0
Assets held for sale	0	0
Prepaid expenses and other current assets	1,089	1,200
Total current assets	(7,949)	(6,341)
Net property and equipment	3,075	3,311
Investments in subsidiaries	626,699	657,090
Intangible assets, net of accumulated amortization	0	0
Deferred income taxes	85,921	84,989
Other long-term assets	392	512
Total assets	708,138	739,561
Current liabilities:
Accounts payable	516	616
Deferred revenues	0	0
Accrued expenses	3,848	8,373
Total current liabilities	4,364	8,989
Long-term debt, less current portion	387,621	387,217
Deferred income taxes	0	0
Other long-term liabilities	1,041	712
Total liabilities	393,026	396,918
Total shareholders' equity	315,112	342,643
Total liabilities and shareholders' equity	$ 708,138	$ 739,561