Net Property, Plant and Equipment (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Property, plant and equipment
Gross property, plant and equipment	$ 1,786,711us-gaap_PropertyPlantAndEquipmentGross	$ 1,777,309us-gaap_PropertyPlantAndEquipmentGross
Accumulated depreciation and amortization	(939,954)	(913,736)
Net property, plant and equipment	846,757us-gaap_PropertyPlantAndEquipmentNet	863,573us-gaap_PropertyPlantAndEquipmentNet
Minimum
Property, plant and equipment
Useful Lives	3 years
Maximum
Property, plant and equipment
Useful Lives	30 years
Land and improvements
Property, plant and equipment
Gross property, plant and equipment	184,647	194,237
Land and improvements \| Minimum
Property, plant and equipment
Useful Lives	0 years
Land and improvements \| Maximum
Property, plant and equipment
Useful Lives	15 years
Buildings and improvements
Property, plant and equipment
Useful Lives	30 years
Gross property, plant and equipment	389,193	395,598
Machinery and equipment
Property, plant and equipment
Gross property, plant and equipment	1,001,061	990,553
Machinery and equipment \| Minimum
Property, plant and equipment
Useful Lives	3 years
Machinery and equipment \| Maximum
Property, plant and equipment
Useful Lives	20 years
Vessels and vehicles
Property, plant and equipment
Gross property, plant and equipment	160,310	126,502
Vessels and vehicles \| Minimum
Property, plant and equipment
Useful Lives	3 years
Vessels and vehicles \| Maximum
Property, plant and equipment
Useful Lives	18 years
Office furniture and fixtures
Property, plant and equipment
Useful Lives	5 years
Gross property, plant and equipment	25,965	30,102
Construction in progress
Property, plant and equipment
Gross property, plant and equipment	$ 25,535	$ 40,317

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 360

-SubTopic 10

-Section 50

-Paragraph 1

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.14)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 14

-Article 5

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- Definition

Amount before accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 360

-SubTopic 10

-Section 50

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

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-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.13)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 360

-SubTopic 10

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.13)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 13

-Subparagraph a

-Article 5

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 8

-Article 7

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- Definition

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+ References

No definition available.

+ Details

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