Condensed Consolidating Financial Information - Balance Sheet (Details) - USD ($) $ in Thousands		Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents		$ 367,039	$ 336,997	$ 200,688	$ 264,093
Short-term investments		26,548	28,369
Accounts receivable, net		733,541	698,477
Inventory, net		174,308	166,307
Assets held for sale		36,404	37,052
Other current assets		156,533	180,134
Total current assets		1,494,373	1,447,336
Property, plant and equipment, net		5,969,063	6,109,565
Goodwill		172,982	173,226
Deferred income taxes		417,781	419,003
Other long-term assets		245,631	252,854
Total assets	[1]	8,299,830	8,401,984
Current liabilities:
Less: current portion		375	181
Trade accounts payable		309,883	363,416
Accrued liabilities		432,294	533,044
Income taxes payable		24,276	22,835
Total current liabilities		766,828	919,476
Long-term debt		4,256,160	4,027,766
Other long-term liabilities		321,652	301,633
Deferred income taxes		11,786	10,338
Total liabilities	[1]	5,356,426	5,259,213
Redeemable noncontrolling interest in subsidiary (Note 3)		206,396	203,998
Shareholders' equity		2,709,608	2,911,816
Noncontrolling interest		27,400	26,957
Total equity		2,737,008	2,938,773	3,186,394	3,254,795
Total liabilities and equity		8,299,830	8,401,984
Consolidating Adjustments
Current assets:
Intercompany receivables		(694,046)	(614,694)
Investment in consolidated affiliates		(11,952,751)	(12,131,052)
Deferred income taxes		(348,436)	(333,349)
Other long-term assets		(26,025)	(72,143)
Total assets		(13,021,258)	(13,151,238)
Current liabilities:
Long-term debt		(26,025)	(72,143)
Deferred income taxes		(348,436)	(333,349)
Intercompany payable		(694,046)	(614,694)
Total liabilities		(1,068,507)	(1,020,186)
Shareholders' equity		(11,952,751)	(12,131,052)
Total equity		(11,952,751)	(12,131,052)
Total liabilities and equity		(13,021,258)	(13,151,238)
Parent Company | Reportable Legal Entities
Current assets:
Cash and cash equivalents		474	1,091	8,579	1,148
Other current assets		50	50
Total current assets		524	1,141
Intercompany receivables		138,120	133,602
Investment in consolidated affiliates		2,592,942	2,799,320
Total assets		2,731,586	2,934,063
Current liabilities:
Trade accounts payable		127	147
Accrued liabilities		21,851	21,100
Total current liabilities		21,978	21,247
Intercompany payable			1,000
Total liabilities		21,978	22,247
Shareholders' equity		2,709,608	2,911,816
Total equity		2,709,608	2,911,816
Total liabilities and equity		2,731,586	2,934,063
Guarantor Subsidiaries | Reportable Legal Entities
Current assets:
Cash and cash equivalents		44	44	4	10,177
Other current assets			56
Total current assets		44	100
Intercompany receivables		555,926	481,092
Investment in consolidated affiliates		5,555,826	5,531,799
Deferred income taxes		348,436	333,349
Other long-term assets		122	78
Total assets		6,460,354	6,346,418
Current liabilities:
Trade accounts payable		36	124
Accrued liabilities		27,785	67,760
Total current liabilities		27,821	67,884
Long-term debt		4,282,185	4,099,909
Other long-term liabilities		16,291	16,284
Total liabilities		4,326,297	4,184,077
Shareholders' equity		2,134,057	2,162,341
Total equity		2,134,057	2,162,341
Total liabilities and equity		6,460,354	6,346,418
Other Subsidiaries (Non-Guarantors) | Reportable Legal Entities
Current assets:
Cash and cash equivalents		366,521	335,862	$ 192,105	$ 252,768
Short-term investments		26,548	28,369
Accounts receivable, net		733,541	698,477
Inventory, net		174,308	166,307
Assets held for sale		36,404	37,052
Other current assets		156,483	180,028
Total current assets		1,493,805	1,446,095
Property, plant and equipment, net		5,969,063	6,109,565
Goodwill		172,982	173,226
Investment in consolidated affiliates		3,803,983	3,799,933
Deferred income taxes		417,781	419,003
Other long-term assets		271,534	324,919
Total assets		12,129,148	12,272,741
Current liabilities:
Less: current portion		375	181
Trade accounts payable		309,720	363,145
Accrued liabilities		382,658	444,184
Income taxes payable		24,276	22,835
Total current liabilities		717,029	830,345
Other long-term liabilities		305,361	285,349
Deferred income taxes		360,222	343,687
Intercompany payable		694,046	613,694
Total liabilities		2,076,658	2,073,075
Redeemable noncontrolling interest in subsidiary (Note 3)		206,396	203,998
Shareholders' equity		9,818,694	9,968,711
Noncontrolling interest		27,400	26,957
Total equity		9,846,094	9,995,668
Total liabilities and equity		$ 12,129,148	$ 12,272,741

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