Amortized cost 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 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 realized gain (loss) on investment in marketable security, including other-than-temporary impairment (OTTI).

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The cash inflow associated with the sale of debt and equity securities classified as available-for-sale securities.

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Significant Accounting Policies - Investment in Marketable Securities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018
Investment in Marketable Securities
Marketable Securities		$ 29,887	$ 28,638
Proceeds from sale of marketable securities	$ 55,100
Realized gain (loss) on investment in marketable securities	$ (3,300)
Fair Value
Investment in Marketable Securities
Marketable Securities		29,887	28,638
Commercial mortgage-backed securities
Investment in Marketable Securities
Marketable Securities		29,887	28,638
Cost basis of commercial mortgage backed securities		27,500	27,500
Equity marketable securities
Investment in Marketable Securities
Cost basis of commercial mortgage backed securities		$ 0	$ 0