Condensed Consolidating Financial Information - Balance Sheet (Details) - USD ($) $ in Thousands		Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents		$ 593,284	$ 336,997	$ 196,567	$ 264,093
Short-term investments		43,262	28,369
Accounts receivable, net		780,247	698,477
Inventory, net		173,063	166,307
Assets held for sale		35,963	37,052
Other current assets		156,652	180,134
Total current assets		1,782,471	1,447,336
Property, plant and equipment, net		5,709,895	6,109,565
Goodwill		172,817	173,226
Deferred income taxes		406,281	419,003
Other long-term assets		228,824	252,854
Total assets (1)	[1]	8,300,288	8,401,984
Current liabilities:
Less: current portion		243	181
Trade accounts payable		379,028	363,416
Accrued liabilities		492,787	533,044
Income taxes payable		1,724	22,835
Total current liabilities		873,782	919,476
Long-term debt		3,818,613	4,027,766
Other long-term liabilities		290,013	301,633
Deferred income taxes		20,713	10,338
Total liabilities (1)	[1]	5,003,121	5,259,213
Redeemable noncontrolling interest in subsidiary (Note 3)		208,519	203,998
Shareholders' equity		3,063,034	2,911,816
Noncontrolling interest		25,614	26,957
Total equity		3,088,648	2,938,773	$ 3,072,778	$ 3,254,795
Total liabilities and equity		8,300,288	8,401,984
Consolidating Adjustments
Current assets:
Short-term investments		54
Total current assets		54
Intercompany receivables		(690,387)	(614,694)
Investment in consolidated affiliates		(12,334,583)	(12,131,052)
Deferred income taxes		(362,463)	(333,349)
Other long-term assets		(26,025)	(72,143)
Total assets (1)		(13,413,404)	(13,151,238)
Current liabilities:
Long-term debt		(26,025)	(72,143)
Deferred income taxes		(362,463)	(333,349)
Intercompany payable		(690,387)	(614,694)
Total liabilities (1)		(1,078,875)	(1,020,186)
Shareholders' equity		(12,334,529)	(12,131,052)
Total equity		(12,334,529)	(12,131,052)
Total liabilities and equity		(13,413,404)	(13,151,238)
Parent Company | Reportable Legal Entities
Current assets:
Cash and cash equivalents		3,182	1,091
Other current assets		50	50
Total current assets		3,232	1,141
Intercompany receivables		107,379	133,602
Investment in consolidated affiliates		2,981,471	2,799,320
Total assets (1)		3,092,082	2,934,063
Current liabilities:
Trade accounts payable		1,006	147
Accrued liabilities		28,042	21,100
Total current liabilities		29,048	21,247
Intercompany payable			1,000
Total liabilities (1)		29,048	22,247
Shareholders' equity		3,063,034	2,911,816
Total equity		3,063,034	2,911,816
Total liabilities and equity		$ 3,092,082	2,934,063
Guarantor Subsidiaries
Condensed Consolidating Financial Information
Ownership percentage		100.00%
Guarantor Subsidiaries | Reportable Legal Entities
Current assets:
Cash and cash equivalents		$ 43	44
Other current assets			56
Total current assets		43	100
Intercompany receivables		583,008	481,092
Investment in consolidated affiliates		5,337,900	5,531,799
Deferred income taxes		362,463	333,349
Other long-term assets		79	78
Total assets (1)		6,283,493	6,346,418
Current liabilities:
Trade accounts payable		175	124
Accrued liabilities		77,098	67,760
Total current liabilities		77,273	67,884
Long-term debt		3,844,638	4,099,909
Other long-term liabilities		16,299	16,284
Total liabilities (1)		3,938,210	4,184,077
Shareholders' equity		2,345,283	2,162,341
Total equity		2,345,283	2,162,341
Total liabilities and equity		6,283,493	6,346,418
Other Subsidiaries (Non-Guarantors) | Reportable Legal Entities
Current assets:
Cash and cash equivalents		590,059	335,862
Short-term investments		43,208	28,369
Accounts receivable, net		780,247	698,477
Inventory, net		173,063	166,307
Assets held for sale		35,963	37,052
Other current assets		156,602	180,028
Total current assets		1,779,142	1,446,095
Property, plant and equipment, net		5,709,895	6,109,565
Goodwill		172,817	173,226
Investment in consolidated affiliates		4,015,212	3,799,933
Deferred income taxes		406,281	419,003
Other long-term assets		254,770	324,919
Total assets (1)		12,338,117	12,272,741
Current liabilities:
Less: current portion		243	181
Trade accounts payable		377,847	363,145
Accrued liabilities		387,647	444,184
Income taxes payable		1,724	22,835
Total current liabilities		767,461	830,345
Other long-term liabilities		273,714	285,349
Deferred income taxes		383,176	343,687
Intercompany payable		690,387	613,694
Total liabilities (1)		2,114,738	2,073,075
Redeemable noncontrolling interest in subsidiary (Note 3)		208,519	203,998
Shareholders' equity		9,989,246	9,968,711
Noncontrolling interest		25,614	26,957
Total equity		10,014,860	9,995,668
Total liabilities and equity		$ 12,338,117	$ 12,272,741

[1] The condensed consolidated balance sheet as of June 30, 2018 and December 31, 2017 include assets and liabilities of variable interest entities. See Note 3—Joint Ventures for additional information.