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Long-term debt (Details)
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0 Months Ended | 1 Months Ended | 6 Months Ended | 6 Months Ended | 1 Months Ended | 0 Months Ended | 0 Months Ended | ||||||||||||||||||||||||||||||||||||||||||||||||
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Jun. 30, 2013
USD ($)
item
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Dec. 31, 2012
USD ($)
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Jun. 30, 2013
Senior unsecured notes, due 2018
USD ($)
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Dec. 31, 2012
Senior unsecured notes, due 2018
USD ($)
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Jun. 30, 2013
Senior unsecured notes, due June 2036
USD ($)
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Jun. 30, 2013
Senior unsecured notes, due June 2036
CAD
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Dec. 31, 2012
Senior unsecured notes, due June 2036
USD ($)
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Dec. 31, 2012
Senior unsecured notes, due June 2036
CAD
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Jun. 30, 2013
Senior unsecured notes, due July 2014
USD ($)
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Dec. 31, 2012
Senior unsecured notes, due July 2014
USD ($)
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Jun. 30, 2013
Series A senior unsecured notes, due August 2015
USD ($)
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Dec. 31, 2012
Series A senior unsecured notes, due August 2015
USD ($)
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Jun. 30, 2013
Series B senior unsecured notes, due August 2017
USD ($)
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Dec. 31, 2012
Series B senior unsecured notes, due August 2017
USD ($)
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Jun. 30, 2013
Epsilon Power Partners term facility, due 2019
USD ($)
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Dec. 31, 2012
Epsilon Power Partners term facility, due 2019
USD ($)
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Jun. 30, 2013
Cadillac term loan, due 2025
USD ($)
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Dec. 31, 2012
Cadillac term loan, due 2025
USD ($)
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Jun. 30, 2013
Cadillac term loan, due 2025
Minimum
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Jun. 30, 2013
Cadillac term loan, due 2025
Maximum
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Apr. 19, 2013
Piedmont bridge loan, due 2013
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Jul. 31, 2013
Piedmont bridge loan, due 2013
USD ($)
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Jun. 30, 2013
Piedmont bridge loan, due 2013
USD ($)
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Dec. 31, 2012
Piedmont bridge loan, due 2013
USD ($)
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Jun. 30, 2013
Senior credit facility
USD ($)
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Jun. 30, 2013
Senior credit facility
Minimum
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Jun. 30, 2013
Senior credit facility
Maximum
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Jun. 30, 2013
Meadow Creek term loan, due 2024
USD ($)
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Dec. 31, 2012
Meadow Creek term loan, due 2024
USD ($)
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Jun. 30, 2013
Meadow Creek term loan, due 2024
Minimum
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Jun. 30, 2013
Meadow Creek term loan, due 2024
Maximum
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Jun. 30, 2013
Construction loan
USD ($)
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Apr. 30, 2013
Cash grant loan
USD ($)
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Jun. 30, 2013
Cash grant loan
USD ($)
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Jun. 30, 2013
Rockland term loan, due 2027
USD ($)
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Dec. 31, 2012
Rockland term loan, due 2027
USD ($)
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Jun. 30, 2013
Rockland term loan, due 2027
Minimum
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Jun. 30, 2013
Rockland term loan, due 2027
Maximum
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Jun. 30, 2013
Other long-term debt
USD ($)
|
Dec. 31, 2012
Other long-term debt
USD ($)
|
Jun. 30, 2013
Other long-term debt
Minimum
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Jun. 30, 2013
Other long-term debt
Maximum
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Aug. 02, 2013
Amended senior credit facility
USD ($)
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Aug. 02, 2013
Amended senior credit facility
US Prime Rate
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Aug. 02, 2013
Amended senior credit facility
Eurocurrency LIBOR Rate
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Aug. 02, 2013
Amended senior credit facility
Cdn. Prime Rate
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Aug. 02, 2013
Amended senior credit facility
Minimum
USD ($)
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Aug. 02, 2013
Amended senior credit facility
Minimum
US Prime Rate
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Aug. 02, 2013
Amended senior credit facility
Minimum
Eurocurrency LIBOR Rate
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Aug. 02, 2013
Amended senior credit facility
Minimum
Cdn. Prime Rate
|
Aug. 02, 2013
Amended senior credit facility
Maximum
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Aug. 02, 2013
Amended senior credit facility
Maximum
US Prime Rate
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Aug. 02, 2013
Amended senior credit facility
Maximum
Eurocurrency LIBOR Rate
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Aug. 02, 2013
Amended senior credit facility
Maximum
Cdn. Prime Rate
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Aug. 02, 2013
5.87% senior guaranteed notes, Series A, due August 15, 2017
USD ($)
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| Long-term debt | |||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Total debt | $ 460,000,000 | $ 460,000,000 | $ 199,700,000 | 210,000,000 | $ 211,100,000 | 210,000,000 | $ 190,000,000 | $ 190,000,000 | $ 150,000,000 | $ 150,000,000 | $ 75,000,000 | $ 75,000,000 | $ 32,000,000 | $ 33,500,000 | $ 36,600,000 | $ 37,800,000 | $ 126,100,000 | $ 127,400,000 | $ 171,400,000 | $ 208,700,000 | $ 172,800,000 | $ 56,500,000 | $ 85,800,000 | $ 86,500,000 | $ 1,100,000 | $ 300,000 | |||||||||||||||||||||||||||||
| Less current maturities | (65,700,000) | (121,200,000) | 4,000,000 | 3,000,000 | 2,200,000 | 2,400,000 | 53,900,000 | 55,100,000 | 4,100,000 | 59,500,000 | 1,400,000 | 1,200,000 | 100,000 | ||||||||||||||||||||||||||||||||||||||||||
| Total long-term debt | 1,462,000,000 | 1,459,100,000 | |||||||||||||||||||||||||||||||||||||||||||||||||||||
| Interest rate (as a percent) | 9.00% | 6.00% | 6.00% | 5.90% | 5.90% | 6.00% | 7.40% | 6.00% | 8.00% | 5.10% | 5.60% | 6.40% | 6.70% | 5.50% | 6.70% | ||||||||||||||||||||||||||||||||||||||||
| Variable interest rate basis | Libor | US Prime Rate | Eurocurrency LIBOR Rate | Cdn. Prime Rate | |||||||||||||||||||||||||||||||||||||||||||||||||||
| Amount drawn on the senior credit facility | 0 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Letters of credit issued but not drawn | 82,500,000 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Applicable margin (as a percent) | 3.50% | 2.75% | 0.80% | 3.00% | 1.75% | 1.75% | 1.75% | 4.75% | 4.75% | 4.75% | |||||||||||||||||||||||||||||||||||||||||||||
| Bridge loan | 51,000,000 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Recovery as a percentage of capital cost | 30.00% | ||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Construction loan | 82,000,000 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Amount received under the 1603 federal grant program | 49,500,000 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Repayment of debt from proceeds from 1603 grant with U.S. Treasury | 51,000,000 | 49,000,000 | |||||||||||||||||||||||||||||||||||||||||||||||||||||
| Number of covenant failures resulting in the non-recourse debt being callable | 0 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Maximum borrowing capacity | 300,000,000 | 150,000,000 | |||||||||||||||||||||||||||||||||||||||||||||||||||||
| Maximum capacity to be utilized for letter of credit | 200,000,000 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Contribution to cover shortfall resulting from the federal sequester on spending | 1,500,000 | 4,700,000 | |||||||||||||||||||||||||||||||||||||||||||||||||||||
| Aggregate amount of sublimit available for borrowings | 25,000,000 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Cash collateralized required if letters of credit and borrowings outstanding under the amended credit facility exceeds $125 million | 125,000,000 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Threshold limit of amended credit facility for required cash collateralized | 125,000,000 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Unrestricted cash and cash equivalents | 75,000,000 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Consolidated Total Net Debt to Consolidated EBITDA | 7.50 | 7.75 | |||||||||||||||||||||||||||||||||||||||||||||||||||||
| Consolidated EBITDA to Consolidated Interest Expense | 2.25 | 1.60 | |||||||||||||||||||||||||||||||||||||||||||||||||||||
| Commitment fee (as a percent) | 1.50% | 0.75% | 1.75% | ||||||||||||||||||||||||||||||||||||||||||||||||||||
| Permissible amount to make voluntary prepayment or repurchases in principal amount | 150,000,000 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Period preceding the maturity of debt for voluntarily prepayment or repurchase of any outstanding debt | 60 days | ||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Contribution to cover shortfall resulting from lower grant-eligible costs | $ 2,800,000 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||