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Investments (Narrative) (Details) - USD ($) | 3 Months Ended | 12 Months Ended |
--- | --- | --- | ---
Mar. 31, 2019 | Mar. 31, 2018 | Dec. 31, 2015 | Dec. 31, 2018
Investments, Debt and Equity Securities [Abstract] |  |  |  |
Technology investments in non-consolidated affiliates (less than) |  |  | 20.00% |
Technology investments in non-consolidated affiliates | $ 4,100,000 |  |  | $ 3,850,000
Equity investment losses were considered to be other than temporary | $ 0 | $ 0 |  |

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