Guarantor/Non Guarantor Condensed Consolidating Financial Statements (Balance Sheet)) (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 30,132		$ 53,566
Restricted cash	998		998
Receivables, net of allowance	145,572		130,881
Intercompany receivable (payable)	0		0
Inventory	22,800		18,898
Assets held for sale	5,962		3,582
Prepaid expenses and other current assets	7,061		7,109
Total current assets	212,525		215,034
Net property and equipment	500,843		524,858
Investments in subsidiaries	0		0
Deferred income taxes	0		0
Operating lease assets	8,775		0
Other noncurrent assets	1,526		1,658
Total assets	723,669		741,550	$ 757,044
Current liabilities:
Accounts payable	41,019		34,134
Deferred revenues	1,420		1,722
Accrued expenses	63,561		68,912
Total current liabilities	106,000		104,768
Long-term debt, less unamortized discount and debt issuance costs	466,093		464,552
Noncurrent operating lease liabilities	6,495		0
Deferred income taxes	4,913		3,688
Other noncurrent liabilities	1,823		3,484
Total liabilities	585,324		576,492
Total shareholders' equity	138,345	$ 150,967	165,058	$ 182,691	$ 200,187	$ 210,096
Total liabilities and shareholders' equity	723,669		741,550
Eliminations [Member]
Current assets:
Cash and cash equivalents	0		0
Restricted cash	0		0
Receivables, net of allowance	568		196
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	568		196
Net property and equipment	0		0
Investments in subsidiaries	(601,090)		(600,065)
Deferred income taxes	(43,490)		(42,585)
Operating lease assets	0
Other noncurrent assets	0		0
Total assets	(644,012)		(642,454)
Current liabilities:
Accounts payable	0		0
Deferred revenues	0		0
Accrued expenses	568		196
Total current liabilities	568		196
Long-term debt, less unamortized discount and debt issuance costs	0		0
Noncurrent operating lease liabilities	0
Deferred income taxes	(43,490)		(42,585)
Other noncurrent liabilities	0		0
Total liabilities	(42,922)		(42,389)
Total shareholders' equity	(601,090)		(600,065)
Total liabilities and shareholders' equity	(644,012)		(642,454)
Guarantor Subsidiaries [Member]
Current assets:
Cash and cash equivalents	0		0
Restricted cash	0		0
Receivables, net of allowance	108,747		95,030
Intercompany receivable (payable)	65,708		67,098
Inventory	11,784		9,945
Assets held for sale	5,962		3,582
Prepaid expenses and other current assets	3,591		3,197
Total current assets	195,792		178,852
Net property and equipment	471,153		494,376
Investments in subsidiaries	31,020		25,370
Deferred income taxes	0		0
Operating lease assets	4,779
Other noncurrent assets	485		511
Total assets	703,229		699,109
Current liabilities:
Accounts payable	32,324		26,795
Deferred revenues	528		95
Accrued expenses	48,063		49,640
Total current liabilities	80,915		76,530
Long-term debt, less unamortized discount and debt issuance costs	0		0
Noncurrent operating lease liabilities	3,034
Deferred income taxes	48,403		46,273
Other noncurrent liabilities	807		1,611
Total liabilities	133,159		124,414
Total shareholders' equity	570,070		574,695
Total liabilities and shareholders' equity	703,229		699,109
Non-Guarantor Subsidiaries [Member]
Current assets:
Cash and cash equivalents	4,541		3,216
Restricted cash	0		0
Receivables, net of allowance	36,088		35,219
Intercompany receivable (payable)	(38,345)		(39,853)
Inventory	11,016		8,953
Assets held for sale	0		0
Prepaid expenses and other current assets	1,169		2,169
Total current assets	14,469		9,704
Net property and equipment	27,661		28,460
Investments in subsidiaries	0		0
Deferred income taxes	0		0
Operating lease assets	643
Other noncurrent assets	425		551
Total assets	43,198		38,715
Current liabilities:
Accounts payable	5,897		6,246
Deferred revenues	892		1,627
Accrued expenses	4,664		5,056
Total current liabilities	11,453		12,929
Long-term debt, less unamortized discount and debt issuance costs	0		0
Noncurrent operating lease liabilities	493
Deferred income taxes	0		0
Other noncurrent liabilities	232		416
Total liabilities	12,178		13,345
Total shareholders' equity	31,020		25,370
Total liabilities and shareholders' equity	43,198		38,715
Parent [Member]
Current assets:
Cash and cash equivalents	25,591		50,350
Restricted cash	998		998
Receivables, net of allowance	169		436
Intercompany receivable (payable)	(27,363)		(27,245)
Inventory	0		0
Assets held for sale	0		0
Prepaid expenses and other current assets	2,301		1,743
Total current assets	1,696		26,282
Net property and equipment	2,029		2,022
Investments in subsidiaries	570,070		574,695
Deferred income taxes	43,490		42,585
Operating lease assets	3,353
Other noncurrent assets	616		596
Total assets	621,254		646,180
Current liabilities:
Accounts payable	2,798		1,093
Deferred revenues	0		0
Accrued expenses	10,266		14,020
Total current liabilities	13,064		15,113
Long-term debt, less unamortized discount and debt issuance costs	466,093		464,552
Noncurrent operating lease liabilities	2,968
Deferred income taxes	0		0
Other noncurrent liabilities	784		1,457
Total liabilities	482,909		481,122
Total shareholders' equity	138,345		165,058
Total liabilities and shareholders' equity	$ 621,254		$ 646,180