Marketable Securities - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Investments, Debt and Equity Securities [Abstract]
Fair market value of investment securities exceeds cost basis	$ 568		$ 568
Unrealized (loss) gain on available-for-sale securities	(68)	$ 17	370	$ 55
Estimated taxes of change in value of available-for-sale securities			79
Gross unrealized holding gains	1		1
Gross unrealized holding losses	$ 569		$ 569

Debt Securities, Available for sale securities, fair market value exceeds cost basis, by amount.

No definition available.

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- Definition

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

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- Definition

Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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- Definition

Amount after tax, before reclassification adjustments, of unrealized holding gain (loss) on available-for-sale securities.

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- Definition

Amount of tax expense (benefit) before reclassification adjustments of unrealized holding gain (loss) on available-for-sale securities.

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