Guarantor/Non Guarantor Condensed Consolidated Financial Statements (Balance Sheet (Unaudited)) (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 14,578	$ 14,160	$ 62,468	$ 34,924
Receivables, net of allowance	58,879	79,816
Intercompany receivable (payable)	0	0
Inventory	8,640	9,262
Assets held for sale	4,513	4,619
Prepaid expenses and other current assets	5,889	7,411
Total current assets	92,499	115,268
Net property and equipment	654,794	702,585
Investments in subsidiaries	0	0
Intangible assets, net of accumulated amortization	1,166	1,944
Deferred income taxes	15	18
Other long-term assets	2,050	2,178
Total assets	750,524	821,993	1,004,897
Current liabilities:
Accounts payable	13,077	16,951
Deferred revenues	2,848	6,222
Accrued expenses	43,294	46,869
Total current liabilities	59,219	70,042
Long-term Debt, Excluding Current Maturities	387,551	387,217
Deferred income taxes	15,100	17,520
Other long-term liabilities	3,508	4,571
Total liabilities	465,378	479,350
Total shareholders' equity	285,146	342,643
Total liabilities and shareholders' equity	750,524	821,993
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	(639,138)	(699,330)
Intangible assets, net of accumulated amortization	0	0
Deferred income taxes	(85,759)	(84,989)
Other long-term assets	0	0
Total assets	(724,897)	(784,319)
Current liabilities:
Accounts payable	0	0
Deferred revenues	0	0
Accrued expenses	0	0
Total current liabilities	0	0
Long-term Debt, Excluding Current Maturities	0	0
Deferred income taxes	(85,759)	(84,989)
Other long-term liabilities	0	0
Total liabilities	(85,759)	(84,989)
Total shareholders' equity	(639,138)	(699,330)
Total liabilities and shareholders' equity	(724,897)	(784,319)
Guarantor Subsidiaries [Member]
Current assets:
Cash and cash equivalents	(1,112)	(5,612)	(2,033)	(5,516)
Receivables, net of allowance	55,960	67,174
Intercompany receivable (payable)	31,628	31,108
Inventory	5,128	5,591
Assets held for sale	4,513	4,619
Prepaid expenses and other current assets	3,038	4,767
Total current assets	99,155	107,647
Net property and equipment	623,236	667,321
Investments in subsidiaries	32,981	42,240
Intangible assets, net of accumulated amortization	1,166	1,944
Deferred income taxes	0	0
Other long-term assets	850	962
Total assets	757,388	820,114
Current liabilities:
Accounts payable	11,870	14,628
Deferred revenues	2,446	5,570
Accrued expenses	33,949	37,023
Total current liabilities	48,265	57,221
Long-term Debt, Excluding Current Maturities	0	0
Deferred income taxes	100,859	102,509
Other long-term liabilities	2,107	3,294
Total liabilities	151,231	163,024
Total shareholders' equity	606,157	657,090
Total liabilities and shareholders' equity	757,388	820,114
Non-Guarantor Subsidiaries [Member]
Current assets:
Cash and cash equivalents	5,162	2,551	6,815	12,752
Receivables, net of allowance	2,556	12,568
Intercompany receivable (payable)	(6,791)	(6,272)
Inventory	3,512	3,671
Assets held for sale	0	0
Prepaid expenses and other current assets	1,206	1,444
Total current assets	5,645	13,962
Net property and equipment	28,729	31,953
Investments in subsidiaries	0	0
Intangible assets, net of accumulated amortization	0	0
Deferred income taxes	15	18
Other long-term assets	763	704
Total assets	35,152	46,637
Current liabilities:
Accounts payable	280	1,707
Deferred revenues	402	652
Accrued expenses	1,079	1,473
Total current liabilities	1,761	3,832
Long-term Debt, Excluding Current Maturities	0	0
Deferred income taxes	0	0
Other long-term liabilities	410	565
Total liabilities	2,171	4,397
Total shareholders' equity	32,981	42,240
Total liabilities and shareholders' equity	35,152	46,637
Parent [Member]
Current assets:
Cash and cash equivalents	10,528	17,221	$ 57,686	$ 27,688
Receivables, net of allowance	363	74
Intercompany receivable (payable)	(24,837)	(24,836)
Inventory	0	0
Assets held for sale	0	0
Prepaid expenses and other current assets	1,645	1,200
Total current assets	(12,301)	(6,341)
Net property and equipment	2,829	3,311
Investments in subsidiaries	606,157	657,090
Intangible assets, net of accumulated amortization	0	0
Deferred income taxes	85,759	84,989
Other long-term assets	437	512
Total assets	682,881	739,561
Current liabilities:
Accounts payable	927	616
Deferred revenues	0	0
Accrued expenses	8,266	8,373
Total current liabilities	9,193	8,989
Long-term Debt, Excluding Current Maturities	387,551	387,217
Deferred income taxes	0	0
Other long-term liabilities	991	712
Total liabilities	397,735	396,918
Total shareholders' equity	285,146	342,643
Total liabilities and shareholders' equity	$ 682,881	$ 739,561