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

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

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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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Investments (Major Categories of Net Investment Gains (Losses) on Investments) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Gain (Loss) on Securities [Line Items]
Investment gains (losses), net	$ 6,817	$ 533	$ 18,754	$ (4,302)
Debt Securities [Member]
Gain (Loss) on Securities [Line Items]
Gain (loss) on investments	60	381	4,201	366
Equity Securities [Member]
Gain (Loss) on Securities [Line Items]
Gain (loss) on equity securities		359		359
Unrealized gains (losses) on equity securities	5,356	553	13,116	(3,904)
Other Investments [Member]
Gain (Loss) on Securities [Line Items]
Unrealized gains (losses) on equity securities	1,401	(401)	1,437	(764)
U.S. Treasury Securities and Obligations of U.S. Government [Member] \| Debt Securities [Member]
Gain (Loss) on Securities [Line Items]
Gain (loss) on investments
Corporate Bonds [Member] \| Debt Securities [Member]
Gain (Loss) on Securities [Line Items]
Gain (loss) on investments	(6)	(14)	17	(22)
Collateralized Corporate Bank Loans [Member] \| Debt Securities [Member]
Gain (Loss) on Securities [Line Items]
Gain (loss) on investments	21	35	38	47
Municipal Bonds [Member] \| Debt Securities [Member]
Gain (Loss) on Securities [Line Items]
Gain (loss) on investments	46	2	4,147	(19)
Mortgage Backed [Member] \| Debt Securities [Member]
Gain (Loss) on Securities [Line Items]
Gain (loss) on investments	$ (1)	$ (1)	$ (1)	$ 1