Condensed Consolidating Guarantor Financial Statements - Balance Sheets (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015	Dec. 31, 2014
Condensed Balance Sheet Statements, Captions [Line Items]
Other Liabilities, Current	$ 11,510	$ 13,281
Current assets:
Cash and cash equivalents	255,780	58,096	$ 228,783	$ 40,598
Restricted cash	31	32
Accounts receivable, net	388,668	326,713
Receivable from affiliates	10,219	5,914
Inventories	85,460	70,239
Other current assets	25,445	19,387
Total current assets	765,603	480,381
Property, plant and equipment, net	1,648,962	1,566,821
Equity method investments	446,938	551,078
Goodwill	34,698	48,032
Other intangible assets, net	156,617	162,223
Other noncurrent assets	44,156	45,374
Total assets	3,096,974	2,853,909
Current liabilities:
Accounts Payable	338,720	273,666
Due to Related Parties	9,030	5,033
Accrued Liabilities	84,703	85,047
Total current liabilities	443,963	377,027
Long-term debt, net	1,070,363	1,057,816
Deferred income taxes	183,776	200,953
Other noncurrent liabilities	23,544	21,757
Commitments and contingencies
Owners’ equity excluding noncontrolling interests in consolidated subsidiaries	1,304,245	1,115,527
Noncontrolling interests in consolidated subsidiaries	71,083	80,829
Total owners’ equity	1,375,328	1,196,356
Total liabilities and owners’ equity	3,096,974	2,853,909
Parent Company [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Other Liabilities, Current	364	569
Current assets:
Cash and cash equivalents	187,987	4,559	118,060	9,254
Restricted cash	0	0
Accounts receivable, net	641	640
Receivable from affiliates	4,897	1,616
Inventories	0	0
Other current assets	9,228	8,477
Total current assets	202,753	15,292
Property, plant and equipment, net	4,915	4,335
Equity method investments	1,502,156	1,546,853
Goodwill	0	0
Other intangible assets, net	18	20
Other noncurrent assets	38,780	39,358
Total assets	1,748,622	1,605,858
Current liabilities:
Accounts Payable	533	734
Due to Related Parties	53	78
Accrued Liabilities	9,392	5,551
Total current liabilities	10,342	6,932
Long-term debt, net	295,875	325,460
Deferred income taxes	135,985	155,411
Other noncurrent liabilities	2,175	2,528
Commitments and contingencies
Owners’ equity excluding noncontrolling interests in consolidated subsidiaries	1,304,245	1,115,527
Noncontrolling interests in consolidated subsidiaries	0	0
Total owners’ equity	1,304,245	1,115,527
Total liabilities and owners’ equity	1,748,622	1,605,858
Guarantor Subsidiaries [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Other Liabilities, Current	0	0
Current assets:
Cash and cash equivalents	0	0	0	0
Restricted cash	0	0
Accounts receivable, net	12,596	20,015
Receivable from affiliates	802	1,119
Inventories	(120)	(48)
Other current assets	742	359
Total current assets	14,020	21,445
Property, plant and equipment, net	532,702	536,628
Equity method investments	510,115	426,801
Goodwill	0	13,052
Other intangible assets, net	140,083	144,183
Other noncurrent assets	778	881
Total assets	1,197,698	1,142,990
Current liabilities:
Accounts Payable	11,346	11,221
Due to Related Parties	21	155
Accrued Liabilities	11,511	10,957
Total current liabilities	22,878	22,333
Long-term debt, net	6,640	7,340
Deferred income taxes	0	0
Other noncurrent liabilities	0	0
Commitments and contingencies
Owners’ equity excluding noncontrolling interests in consolidated subsidiaries	1,168,180	1,113,317
Noncontrolling interests in consolidated subsidiaries	0	0
Total owners’ equity	1,168,180	1,113,317
Total liabilities and owners’ equity	1,197,698	1,142,990
Non-Guarantor Subsidiaries [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Other Liabilities, Current	11,146	12,712
Current assets:
Cash and cash equivalents	68,614	55,101	112,980	35,445
Restricted cash	31	32
Accounts receivable, net	375,431	306,058
Receivable from affiliates	9,467	6,141
Inventories	85,580	70,287
Other current assets	15,475	10,551
Total current assets	554,598	448,170
Property, plant and equipment, net	1,111,345	1,025,858
Equity method investments	427,961	438,291
Goodwill	34,698	34,980
Other intangible assets, net	16,516	18,020
Other noncurrent assets	4,598	5,135
Total assets	2,149,716	1,970,454
Current liabilities:
Accounts Payable	326,841	261,711
Due to Related Parties	13,903	7,762
Accrued Liabilities	63,796	68,534
Total current liabilities	415,686	350,719
Long-term debt, net	790,988	748,856
Deferred income taxes	47,791	45,542
Other noncurrent liabilities	21,369	19,229
Commitments and contingencies
Owners’ equity excluding noncontrolling interests in consolidated subsidiaries	802,799	725,279
Noncontrolling interests in consolidated subsidiaries	71,083	80,829
Total owners’ equity	873,882	806,108
Total liabilities and owners’ equity	2,149,716	1,970,454
Consolidating Adjustments [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Other Liabilities, Current	0	0
Current assets:
Cash and cash equivalents	(821)	(1,564)	$ (2,257)	$ (4,101)
Restricted cash	0	0
Accounts receivable, net	0	0
Receivable from affiliates	(4,947)	(2,962)
Inventories	0	0
Other current assets	0	0
Total current assets	(5,768)	(4,526)
Property, plant and equipment, net	0	0
Equity method investments	(1,993,294)	(1,860,867)
Goodwill	0	0
Other intangible assets, net	0	0
Other noncurrent assets	0	0
Total assets	(1,999,062)	(1,865,393)
Current liabilities:
Accounts Payable	0	0
Due to Related Parties	(4,947)	(2,962)
Accrued Liabilities	4	5
Total current liabilities	(4,943)	(2,957)
Long-term debt, net	(23,140)	(23,840)
Deferred income taxes	0	0
Other noncurrent liabilities	0	0
Commitments and contingencies
Owners’ equity excluding noncontrolling interests in consolidated subsidiaries	(1,970,979)	(1,838,596)
Noncontrolling interests in consolidated subsidiaries	0	0
Total owners’ equity	(1,970,979)	(1,838,596)
Total liabilities and owners’ equity	$ (1,999,062)	$ (1,865,393)