Fair Value Measurements - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Unrealized gain (loss) on available-for-sale marketable securities, net of taxes	$ 1,416	$ (1,138)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Proceeds from available for sale municipal bonds	3,539	2,467
Realized gain	100
Realized loss		100
Unrealized gains related to equity securities	3,400	300
Municipal bonds — available-for-sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Proceeds from available for sale municipal bonds	$ 3,500	$ 2,400

Amount of unrealized gain before deducting unrealized loss on investments in equity securities classified as available-for-sale securities.

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-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
-Section 50
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Amount of realized gain on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
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Amount of realized loss 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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Amount after tax, before reclassification adjustments, of unrealized holding gain (loss) on available-for-sale securities.

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Amount of cash inflow from sale of 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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