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Long-term debt (Details) (USD $) In Millions, unless otherwise specified |  |  |  |  |  |  | 0 Months Ended |
--- | --- | --- | --- | --- | --- | --- | --- | ---
Sep. 30, 2014 | Dec. 31, 2013 | Jul. 15, 2014 The Company [Member] | May 08, 2014 The Company [Member] | Apr. 15, 2014 The Company [Member] | Jan. 28, 2014 The Company [Member] | Apr. 02, 2014 Centennial Energy Holdings, Inc [Member] | Mar. 31, 2014 Centennial Energy Holdings, Inc [Member] | May 08, 2014 Centennial Energy Holdings, Inc [Member]
Line of Credit Facility [Line Items] |  |  |  |  |  |  |  |  |
Note purchase agreement |  |  |  |  |  | $ 150.0 |  |  |
Senior notes issued |  |  | 100.0 |  | 50.0 |  |  |  |
Senior notes weighted average interest rate |  |  | 4.30% |  | 5.20% |  |  |  |
Facility, maximum borrowing capacity |  |  |  | 175.0 |  |  |  |  | 650.0
Ratio of total debt to total capitalization as specified in debt convenants |  |  |  |  |  |  | 65.00% | 65.00% | 65.00%
Debt instrument, term |  |  |  |  |  |  | 2 years | 2 years |
Term loan agreement |  |  |  |  |  |  | 125.0 | 125.0 |
Long-term commercial paper | $ 293.5 | $ 153.9 |  |  |  |  |  |  |

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- Definition Note purchase agreement. + References No definition available. + Details
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- Definition Ratio of total debt to total capitalization as specified in debt convenants. + References No definition available. + Details
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- Definition Senior notes issued. + References No definition available. + Details
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- Definition Weighted average interest rate of senior notes issued. + References No definition available. + Details
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- Definition Term loan agreement. + References No definition available. + Details
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- Definition Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
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- Details
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- Definition 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 -Section 02 -Paragraph 19, 22 -Article 5 + Details
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- Definition Including the current and noncurrent portions, carrying value as of the balance sheet date of long-term unsecured obligations issued by corporations and other borrowers to investors (with maturities initially due after one year or beyond the operating cycle if longer). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 20 -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 19 -Article 5 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.16) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.16) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19,20,22) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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