Investments (Major Categories of Net Investment Gains (Losses) on Investments) (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Gain (Loss) on Securities [Line Items]
Gain on investments	$ 4,464	$ 1,803
Investment gains (losses), net	20,618	(10,195)
Equity Securities [Member]
Gain (Loss) on Securities [Line Items]
Gain (loss) on equity securities	(7)	359
Unrealized gains (losses) on equity securities	15,133	(9,322)
Other Investments [Member]
Gain (Loss) on Securities [Line Items]
Unrealized gains (losses) on equity securities	1,021	(2,676)
Corporate Bonds [Member] \| Debt Securities [Member]
Gain (Loss) on Securities [Line Items]
Gain (loss) on debt securities	235	(83)
Collateralized Corporate Bank Loans [Member] \| Debt Securities [Member]
Gain (Loss) on Securities [Line Items]
Gain (loss) on debt securities	(34)	90
Municipal Bonds [Member] \| Debt Securities [Member]
Gain (Loss) on Securities [Line Items]
Gain (loss) on debt securities	$ 4,270	1,435
Mortgage Backed [Member] \| Debt Securities [Member]
Gain (Loss) on Securities [Line Items]
Gain (loss) on debt securities		$ 2

Amount of unrealized and realized gain (loss) on investment in debt and equity securities.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(9)(a))
-URI http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227

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+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
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Amount of realized gain (loss) from sale of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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Amount of unrealized gain (loss) on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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