v3.19.1

Summary of significant accounting policies - Marketable securities (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Summary of significant accounting policies
Short-term marketable securities	$ 36,888	$ 0
Unrealized gains, net of tax in accumulated other comprehensive loss	16
Income tax effect related to unrealized gains in accumulated other comprehensive loss	$ 0

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Accumulated unrealized gain (loss), after tax, 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 of investment in debt and equity securities categorized neither as trading securities nor held-to-maturity securities and intended be sold or mature one year or operating cycle, if longer.

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