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Investment Securities (Narrative) (Details) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended |
--- | --- | --- | ---
Jun. 30, 2018 | Jun. 30, 2018 | Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract] |  |  |
Carrying amount of equity investments without a readily determinable fair value | $ 16.4 | $ 16.4 | $ 16.3
Unrealized gain for equity investments with readily determinable fair values | $ 0.7 | $ 1.1 |

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- Definition Equity Securities without Readily Determinable Fair Value, Amount + References No definition available. + Details
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