Supplemental Guarantor Information (Condensed Consolidating Balance Sheets) (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 259,889			$ 158,050
Accounts receivable, net	368,530			447,353
Other current assets	204,600			167,502
Total current assets	833,019			772,905
Property, plant and equipment, net	891,540			1,109,126
Operating lease right-of-use assets	96,190
Goodwill	135,922			136,788
Notes receivable	67,042			63,993
Restricted cash	2,753			5,698
Intangible and other long-term assets, net	97,285			127,452
Total assets	2,123,751			2,215,962
Current liabilities:
Accounts payable	110,398			139,325
Accrued expenses	220,623			219,180
Income taxes payable	3,842			734
Current portion of decommissioning liabilities	3,621			3,538
Total current liabilities	338,484			362,777
Long-term debt, net	1,285,755			1,282,921
Decommissioning liabilities	131,263			126,558
Operating lease liabilities	76,255
Other long-term liabilities	148,907			152,967
Total stockholders' equity	143,087	$ 180,391	$ 248,066	290,739	$ 1,036,016	$ 1,052,715	$ 1,078,169	$ 1,132,429
Total liabilities and stockholders' equity	2,123,751			2,215,962
Eliminations [Member]
Current assets:
Intercompany accounts receivable				(90,674)
Total current assets				(90,674)
Long-term intercompany accounts receivable	(7,077,594)			(4,417,627)
Intercompany notes receivable	(7,200)
Equity investments of consolidated subsidiaries	(1,595,695)			(1,808,232)
Total assets	(8,680,489)			(6,316,533)
Current liabilities:
Intercompany accounts payable				(90,674)
Total current liabilities				(90,674)
Long-term intercompany accounts payable	(7,077,594)			(4,417,627)
Intercompany notes payable	(7,200)
Total stockholders' equity	(1,595,695)			(1,808,232)
Total liabilities and stockholders' equity	(8,680,489)			(6,316,533)
Parent [Member]
Current assets:
Long-term intercompany accounts receivable	2,256,701			2,243,431
Equity investments of consolidated subsidiaries	(2,113,614)			(1,952,647)
Total assets	143,087			290,784
Current liabilities:
Accrued expenses				45
Total current liabilities				45
Total stockholders' equity	143,087			290,739
Total liabilities and stockholders' equity	143,087			290,784
Issuer [Member]
Current assets:
Cash and cash equivalents	187,979			102,224
Accounts receivable, net	30			160
Intercompany accounts receivable				12,279
Other current assets	8,592			12,805
Total current assets	196,601			127,468
Property, plant and equipment, net	11,372			10,129
Operating lease right-of-use assets	22,530
Long-term intercompany accounts receivable	1,111,335
Intercompany notes receivable	1,200
Equity investments of consolidated subsidiaries	3,701,545			3,754,887
Intangible and other long-term assets, net	19,203			19,255
Total assets	5,063,786			3,911,739
Current liabilities:
Accounts payable	8,986			8,807
Accrued expenses	80,810			102,845
Income taxes payable	(717)			1,237
Intercompany accounts payable				724
Total current liabilities	89,079			113,613
Long-term debt, net	1,285,755			1,282,921
Deferred income taxes	(149,512)
Operating lease liabilities	23,093
Long-term intercompany accounts payable	5,876,786			4,417,627
Intercompany notes payable	6,000
Other long-term liabilities	46,199			50,225
Total stockholders' equity	(2,113,614)			(1,952,647)
Total liabilities and stockholders' equity	5,063,786			3,911,739
Guarantor Subsidiaries [Member]
Current assets:
Cash and cash equivalents	1,341			707
Accounts receivable, net	280,704			367,497
Intercompany accounts receivable				74,906
Other current assets	133,669			111,560
Total current assets	415,714			554,670
Property, plant and equipment, net	722,830			920,978
Operating lease right-of-use assets	57,334
Goodwill	80,544			80,544
Notes receivable	67,042			63,993
Long-term intercompany accounts receivable	3,491,267			1,991,912
Equity investments of consolidated subsidiaries	7,764			5,992
Restricted cash	2,708			5,653
Intangible and other long-term assets, net	71,239			100,847
Total assets	4,916,442			3,724,589
Current liabilities:
Accounts payable	67,127			109,903
Accrued expenses	104,122			86,926
Intercompany accounts payable				6,869
Total current liabilities	171,249			203,698
Deferred income taxes	145,416
Decommissioning liabilities	131,263			126,558
Operating lease liabilities	42,009
Long-term intercompany accounts payable	1,082,435
Other long-term liabilities	76,510			76,543
Total stockholders' equity	3,267,560			3,317,790
Total liabilities and stockholders' equity	4,916,442			3,724,589
Non-Guarantor Subsidiaries [Member]
Current assets:
Cash and cash equivalents	70,569			55,119
Accounts receivable, net	87,796			79,696
Intercompany accounts receivable				3,489
Other current assets	62,339			43,137
Total current assets	220,704			181,441
Property, plant and equipment, net	157,338			178,019
Operating lease right-of-use assets	16,326
Goodwill	55,378			56,244
Long-term intercompany accounts receivable	218,291			182,284
Intercompany notes receivable	6,000
Restricted cash	45			45
Intangible and other long-term assets, net	6,843			7,350
Total assets	680,925			605,383
Current liabilities:
Accounts payable	34,285			20,615
Accrued expenses	35,691			29,364
Income taxes payable	4,559			(503)
Intercompany accounts payable				83,081
Current portion of decommissioning liabilities	3,621			3,538
Total current liabilities	78,156			136,095
Deferred income taxes	4,096
Operating lease liabilities	11,153
Long-term intercompany accounts payable	118,373
Intercompany notes payable	1,200
Other long-term liabilities	26,198			26,199
Total stockholders' equity	441,749			443,089
Total liabilities and stockholders' equity	$ 680,925			$ 605,383