Stock-Based Compensation (Narrative) (Details) - USD ($) $ in Millions	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017
Fully Vested On The Grant Date [Member] \| Director \| Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share Based Compensation Expense, that vested immediately	$ 1.0	$ 0.8

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

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