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Fair Value of Financial Instruments (Details) - USD ($) $ in Millions | Sep. 30, 2015 | Aug. 18, 2014 | Dec. 21, 2012 | Oct. 17, 2012
--- | --- | --- | --- | ---
Debt Instrument [Line Items] |  |  |  |
Fair value of notes | $ 914.7 |  |  |
October Notes [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Unamortized discount | 2.6 |  |  |
December Notes [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Unamortized premium | 0.3 |  |  |
August Notes [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Unamortized premium | 15.3 |  |  |
Senior Notes [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Carrying value of debt | $ 963.0 |  |  |
Unamortized discount |  |  |  | $ 3.7
Unamortized premium |  | $ 18.0 | $ 0.5 |

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- Definition Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=49121117&loc=d3e13433-108611 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=49121117&loc=d3e13476-108611 + Details
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- Definition The amount of debt discount that was originally recognized at the issuance of the instrument that has yet to be amortized. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 1A -URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28541-108399 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 55 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=34725769&loc=d3e28878-108400 + Details
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- Definition The amount of debt premium that was originally recognized at the issuance of the instrument that has yet to be amortized. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 1A -URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28541-108399 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 55 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=34725769&loc=d3e28878-108400 + Details
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