Investments - Net Investment Income (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Net investment income
Interest income	$ 2,254	$ 2,149	$ 6,755	$ 6,242
Dividend income	104	109	261	354
Investment expense	(122)	(120)	(367)	(309)
Net investment income	$ 2,236	$ 2,138	$ 6,649	$ 6,287

Amount of dividend income on nonoperating securities.

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Amount before accretion (amortization) of purchase discount (premium) of interest income on nonoperating securities.

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Amount of expenses related to the generation of investment income.

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Amount after accretion (amortization) of discount (premium), and investment expense, of interest income and dividend income on nonoperating securities.

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