Investments - Gains and proceeds (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2019	Jun. 30, 2018
Investments
Gain (Loss) on sale of investments	$ 0	$ 2	$ 1,086
Proceeds from sale of available-for-sale debt securities		1,200	64,600
Maturities of investments - debt securities		7,000
Maximum
Investments
Gain (Loss) on sale of investments		100
Purchases of investments - debt securities		$ 100	$ 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 to acquire 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 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).

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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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