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FAIR VALUE OF FINANCIAL INSTRUMENTS (Details 2) (USD $)
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12 Months Ended | 0 Months Ended | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
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Dec. 31, 2012
|
Dec. 31, 2012
9.0 percent notes
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Feb. 02, 2013
9.0 percent notes
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Jan. 17, 2013
9.0 percent notes
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Oct. 12, 2012
9.0 percent notes
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Dec. 31, 2012
9.0 percent notes
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Dec. 31, 2011
9.0 percent notes
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Dec. 31, 2012
Carrying Amount
Level 1
9.0 percent notes
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Dec. 31, 2011
Carrying Amount
Level 1
9.0 percent notes
|
Dec. 31, 2012
Carrying Amount
Level 2
|
Dec. 31, 2011
Carrying Amount
Level 2
|
Dec. 31, 2012
Fair Value
Level 1
9.0 percent notes
|
Dec. 31, 2011
Fair Value
Level 1
9.0 percent notes
|
Dec. 31, 2012
Fair Value
Level 2
|
Dec. 31, 2011
Fair Value
Level 2
|
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| Carrying amount and estimated fair values of fixed-rate long-term debt and natural gas forward purchase contracts | |||||||||||||||
| Interest rate (as a percent) | 9.00% | 9.00% | |||||||||||||
| Face amount of debt | $ 450,000,000 | $ 50,000,000 | |||||||||||||
| Make whole payment included in redemption price | 55,400,000 | ||||||||||||||
| Percentage of the aggregate principal amount of notes redeemed | 99.30% | ||||||||||||||
| Redemption price | 502,300,000 | 51,500,000 | |||||||||||||
| Percentage of the remaining principal amount of notes redeemable | 0.70% | ||||||||||||||
| Long-term debt | 448,091,000 | 497,463,000 | 501,750,000 | 525,315,000 | |||||||||||
| Long-term debt | 448,100,000 | 497,500,000 | |||||||||||||
| Natural gas forward purchase contracts liability | $ (6,000) | $ 721,000 | $ (6,000) | $ 721,000 | |||||||||||
| Redeemable percentage of investment in the fund | 100.00% | ||||||||||||||
| Liquidation of the investment in the fund as a percentage of investment balance at the end of the year | 100.00% | ||||||||||||||
| Holding period of investment | 100 days | ||||||||||||||
| Quarterly liquidation restriction as a percentage of investment balance at the end of the year | 25.00% | ||||||||||||||