Condensed Consolidating Financial Information - Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 336,997	$ 264,093	$ 254,530	$ 501,149
Short-term investments	28,369	31,109
Accounts receivable, net	698,477	508,355
Inventory, net	166,307	103,595
Assets held for sale	37,052	76,668
Other current assets	180,134	172,019
Total current assets	1,447,336	1,155,839
Property, plant and equipment, net	6,109,565	6,267,583	7,027,802
Goodwill	173,226	166,917	166,659
Deferred income taxes	419,003	366,586
Other long-term assets	252,854	230,090
Total assets	8,401,984	8,187,015
Current liabilities:
Less: current portion	181	297
Trade accounts payable	363,416	264,578
Accrued liabilities	533,044	543,248
Income taxes payable	22,835	13,811
Total current liabilities	919,476	821,934
Long-term debt	4,027,766	3,578,335
Other long-term liabilities	301,633	522,456
Deferred income taxes	10,338	9,495
Total liabilities	5,259,213	4,932,220
Redeemable noncontrolling interest in subsidiary (Note 14)	203,998
Shareholders' equity	2,911,816	3,247,025
Noncontrolling interest	26,957	7,770
Total equity	2,938,773	3,254,795	4,293,868	4,918,789
Total liabilities and equity	8,401,984	8,187,015
Consolidating Adjustments
Current assets:
Intercompany receivables	(614,694)	(1,485,390)
Investment in consolidated affiliates	(12,131,052)	(9,084,774)
Deferred income taxes	(333,349)	(443,049)
Other long-term assets	(72,143)	(218,216)
Total assets	(13,151,238)	(11,231,429)
Current liabilities:
Long-term debt	(72,143)	(218,215)
Deferred income taxes	(333,349)	(443,049)
Intercompany payable	(614,694)	(1,485,390)
Total liabilities	(1,020,186)	(2,146,654)
Shareholders' equity	(12,131,052)	(9,084,775)
Total equity	(12,131,052)	(9,084,775)
Total liabilities and equity	(13,151,238)	(11,231,429)
Parent Company | Reportable Legal Entities
Current assets:
Cash and cash equivalents	1,091	1,148	873	1,170
Other current assets	50	50
Total current assets	1,141	1,198
Intercompany receivables	133,602	142,448
Investment in consolidated affiliates	2,799,320	3,170,254
Total assets	2,934,063	3,313,900
Current liabilities:
Trade accounts payable	147	205
Accrued liabilities	21,100	20,669
Total current liabilities	21,247	20,874
Intercompany payable	1,000	46,000
Total liabilities	22,247	66,874
Shareholders' equity	2,911,816	3,247,026
Total equity	2,911,816	3,247,026
Total liabilities and equity	2,934,063	3,313,900
Guarantor Subsidiaries | Reportable Legal Entities
Current assets:
Cash and cash equivalents	44	10,177	10	7
Other current assets	56	22,209
Total current assets	100	32,386
Intercompany receivables	481,092
Investment in consolidated affiliates	5,531,799	4,830,572
Deferred income taxes	333,349	443,049
Other long-term assets	78	344
Total assets	6,346,418	5,306,351
Current liabilities:
Trade accounts payable	124	8
Accrued liabilities	67,760	65,246
Total current liabilities	67,884	65,254
Long-term debt	4,099,909	3,796,550
Other long-term liabilities	16,284	22,659
Intercompany payable		1,439,390
Total liabilities	4,184,077	5,323,853
Shareholders' equity	2,162,341	(17,502)
Total equity	2,162,341	(17,502)
Total liabilities and equity	6,346,418	5,306,351
Other Subsidiaries (Non-Guarantors) | Reportable Legal Entities
Current assets:
Cash and cash equivalents	335,862	252,768	$ 253,647	$ 499,972
Short-term investments	28,369	31,109
Accounts receivable, net	698,477	508,355
Inventory, net	166,307	103,595
Assets held for sale	37,052	76,668
Other current assets	180,028	149,760
Total current assets	1,446,095	1,122,255
Property, plant and equipment, net	6,109,565	6,267,583
Goodwill	173,226	166,917
Intercompany receivables		1,342,942
Investment in consolidated affiliates	3,799,933	1,083,948
Deferred income taxes	419,003	366,586
Other long-term assets	324,919	447,962
Total assets	12,272,741	10,798,193
Current liabilities:
Less: current portion	181	297
Trade accounts payable	363,145	264,365
Accrued liabilities	444,184	457,333
Income taxes payable	22,835	13,811
Total current liabilities	830,345	735,806
Other long-term liabilities	285,349	499,797
Deferred income taxes	343,687	452,544
Intercompany payable	613,694
Total liabilities	2,073,075	1,688,147
Redeemable noncontrolling interest in subsidiary (Note 14)	203,998
Shareholders' equity	9,968,711	9,102,276
Noncontrolling interest	26,957	7,770
Total equity	9,995,668	9,110,046
Total liabilities and equity	$ 12,272,741	$ 10,798,193