Summary of Investments (Net Realized Investment Gains and Losses and Proceeds) (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Gain (Loss) on Securities [Line Items]
Net realized investment gains (losses)	$ 26,713	$ (7,864)
Debt Securities, Available-for-sale [Abstract]
Proceeds from sale of available-for-sale investments	36,490	0
Gross realized gains	30	0
Gross realized losses	13	0
Fixed Maturities \| Available-for-sale
Gain (Loss) on Securities [Line Items]
Net realized investment gains (losses)	150	4
Fixed Maturities \| Change in fair value
Gain (Loss) on Securities [Line Items]
Net realized investment gains (losses)	1,746	(111)
Fixed Maturities \| Sales
Gain (Loss) on Securities [Line Items]
Net realized investment gains (losses)	0	556
Equity securities \| Change in fair value
Gain (Loss) on Securities [Line Items]
Net realized investment gains (losses)	24,634	(9,188)
Equity securities \| Sales
Gain (Loss) on Securities [Line Items]
Net realized investment gains (losses)	198	875
Mortgages
Gain (Loss) on Securities [Line Items]
Net realized investment gains (losses)	(15)	0
Continuing and Discontinuing Operations
Gain (Loss) on Securities [Line Items]
Net realized investment gains (losses)	26,713	(8,921)
Discontinued Operations
Gain (Loss) on Securities [Line Items]
Net realized investment gains (losses)	$ 0	$ (1,057)

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Amount of realized gain 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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