CONSOLIDATED STATEMENTS OF CASH FLOWS INFORMATION (Narrative) (Details) (USD $)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Consolidated Cash Flow Information [Line Items]
Capital expenditures incurred not yet paid	$ 2,600,000	$ 2,400,000	$ 3,500,000
Fees and expenses related to the amendment	1,060,000us-gaap_PaymentsOfDebtIssuanceCosts	1,258,000us-gaap_PaymentsOfDebtIssuanceCosts	23,000us-gaap_PaymentsOfDebtIssuanceCosts
Revolving Credit Facility
Consolidated Cash Flow Information [Line Items]
Maximum borrowing capacity	350,000,000	350,000,000
Line Of Credit Term A Loan
Consolidated Cash Flow Information [Line Items]
Maximum borrowing capacity	150,000,000	50,000,000
Credit Facility Accordion Feature
Consolidated Cash Flow Information [Line Items]
Maximum borrowing capacity	$ 75,000,000	$ 75,000,000

Future cash outflow to pay for purchases of fixed assets that have occurred.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 50

-Paragraph 5

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 50

-Paragraph 4

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

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-Section 50

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Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.19(b),22(b))

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

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

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-Article 5

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The cash outflow paid to third parties in connection with debt origination, which will be amortized over the remaining maturity period of the associated long-term debt.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

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