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Investments (Tables) | 12 Months Ended
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Dec. 31, 2018
Investments [Abstract] |
Unrealized Gain (Loss) on Investments [Table Text Block] | The following table summarizes unrealized gains and losses related to these investments as of December 31, 2018 and December 31, 2017:
Dollar amounts in millions | Amortized Cost |  | Gross Unrealized Gains |  | Gross Unrealized Losses |  | Fair Value
December 31, 2018 | $ | 0.4 |  |  | $ | 5.7 |  |  | $ | — |  |  | $ | 6.1 |
December 31, 2017 | $ | 0.4 |  |  | $ | 5.6 |  |  | $ | — |  |  | $ | 6.0 |

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- Definition Tabular disclosure of unrealized gains and losses on investments. + References No definition available. + Details
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