Investments (Net Realized Gains (Losses) on Disposals) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Schedule of Realized Gains (Losses) on Disposals Excluding OTTI [Line Items]
HTM fixed income securities Gains	$ 0	$ 0	$ 2	$ 44
HTM fixed income securities Losses	0	0	0	(1)
Equity securities Gains	10,584		20,209
Equity securities Losses	(1,919)		(2,249)
Short-term investments Gains	3	0	6	2
Short-term investments Losses	(1)	0	(5)	(2)
Other investments Gains	0	0	0	480
Other investments Losses	(5)	0	(5)	(19)
Net realized investment (losses) gains on disposals	(751)	6,871	4,034	12,252
Sale of fixed income securities, available-for-sale	444,400	94,900	1,382,677	811,991
Sale of equity securities	36,100		79,676
Sale of equity securities, available-for-sale		12,700		19,007
Fixed Maturities [Member]
Schedule of Realized Gains (Losses) on Disposals Excluding OTTI [Line Items]
AFS securities Gains	462	2,070	5,056	8,337
AFS securities Losses	(9,875)	(74)	(18,980)	(1,814)
Equity Securities [Member]
Schedule of Realized Gains (Losses) on Disposals Excluding OTTI [Line Items]
AFS securities Gains		4,875		5,225
AFS securities Losses		0		0
Net realized investment (losses) gains on disposals	$ 8,665	$ 4,875	$ 17,960	$ 5,225

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The cash inflow associated with the sale of equity securities.

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Gross realized gains on short term investments.

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

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Amount of realized gain 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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