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Advanced Technology Costs and Other Income (Narrative) (Details) (USD $) In Millions, unless otherwise specified | 3 Months Ended | 12 Months Ended | 22 Months Ended
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Dec. 31, 2013 | Sep. 30, 2013 | Jun. 30, 2013 | Mar. 31, 2013 | Dec. 31, 2012 | Sep. 30, 2012 | Jun. 30, 2012 | Mar. 31, 2012 | Dec. 31, 2013 | Dec. 31, 2012 | Dec. 31, 2011 | Apr. 14, 2014
RD&D Program Qualifying Expenditures - DOE Share | $ 30.1 | $ 35.9 | $ 40.7 | $ 47.6 | $ 47.5 | $ 34.6 | $ 10.0 | $ 0 | $ 154.3 | $ 92.1 | $ 3.7 |
Maximum funding for RD&D Program |  |  |  |  |  |  |  |  |  |  |  | 350
Maximum RD&D Program Funding by DOE |  |  |  |  |  |  |  |  |  |  |  | 280
RD&D Program Funding by DOE |  |  |  |  |  |  |  |  |  |  |  | 80.00%
RD&D Program Funding by USEC |  |  |  |  |  |  |  |  |  |  |  | 20.00%
RD&D Program Funding by DOE To Date |  |  |  |  |  |  |  |  |  |  |  | 279.6
RD&D Program Funding by DOE - Increment 1 |  |  |  |  |  |  |  |  |  |  |  | 87.7
RD&D Program Funding by DOE - Increment 2 |  |  |  |  |  |  |  |  |  |  |  | 45.7
RD&D Program Funding by DOE - Increment 3 |  |  |  |  |  |  |  |  |  |  |  | 44.4
RD&D Program Funding by DOE - Increment 4 |  |  |  |  |  |  |  |  |  |  |  | 49.9
RD&D Program Funding by DOE - Increment 5 |  |  |  |  |  |  |  |  |  |  |  | 13.6
RD&D Program Funding by DOE - Increment 6 |  |  |  |  |  |  |  |  |  |  |  | 15.7
RD&D Program Funding by DOE - Increment 7 |  |  |  |  |  |  |  |  |  |  |  | 22.6
RD&D Program Qualifying Expenditures To Date | 307.8 |  |  |  |  |  |  |  | 307.8 |  |  |
RD&D Program Qualifying Expenditures To Date - DOE Share | 246.3 |  |  |  |  |  |  |  | 246.3 |  |  |
RD&D Program Qualifying Expenditures To Date - DOE Share - Received | 226.2 |  |  |  |  |  |  |  | 226.2 |  |  |
RD&D Program Qualifying Expenditures To Date - DOE Share - Receivable | 20.1 |  |  |  | 4.4 |  |  |  | 20.1 | 4.4 |  |
RD&D Program Funding - DOE Advance | $ 0 |  |  |  | $ 2.4 |  |  |  | $ 0 | $ 2.4 |  |

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