Short-term Investment Securities (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Short-term investment securities	$ 104,228		$ 104,228		$ 102,789
Unrealized gain (loss), net of deferred taxes	98	$ 101	228	$ 78
Tax effect of the unrealized gain (loss) on short-term investment securities	29	$ 33	67	$ 26
Accumulated other comprehensive income (loss)	(864)		$ (864)		(1,193)
Available-for-sale Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Weighted-average fixed rate			2.40%
Accumulated other comprehensive income (loss)	$ 154		$ 154		$ 74

Interest Income, Weighted-Average Fixed Rate

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Accumulated change in equity from transactions and other events and circumstances from non-owner sources, net of tax effect, at period end. Excludes Net Income (Loss), and accumulated changes in equity from transactions resulting from investments by owners and distributions to owners. Includes foreign currency translation items, certain pension adjustments, unrealized gains and losses on certain investments in debt and equity securities, other than temporary impairment (OTTI) losses related to factors other than credit losses on available-for-sale and held-to-maturity debt securities that an entity does not intend to sell and it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis, as well as changes in the fair value of derivatives related to the effective portion of a designated cash flow hedge.

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), classified as current.

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

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

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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.

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