Investments - Gains and Proceeds (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Investments
Realized loss (gain) on sale of investments	$ (100)	$ (100)
Proceeds from sale of available-for-sale debt securities	1,200	4,000
Maturities of investments - debt securities	11,000	7,000	$ 10,000
Purchases of available-for-sale securities	$ 58,900	$ 100

Amount of realized gain (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 of cash outflow for purchase of marketable security.

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Amount of cash inflow from maturity, prepayment and call of 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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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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