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Realized And Unrealized Investment Gains (Losses) on Investments (Change in Unrealized Gains (Losses) of Available For Sales Securities) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Jan. 01, 2018	Dec. 31, 2017
Realized and Unrealized Investment Gains Losses [Line Items]
Total change in unrealized investment (losses) gains	$ (96,828)	$ (8,563)	$ (298,164)	$ 50,148
Income tax benefit (expense)	2,086	423	45,280	(23,550)
Noncontrolling interests	60	5	86	19
Total change in unrealized gains	(94,682)	(8,135)	(252,798)	26,617
Increase (decrease) in accumulated other comprehensive income	(474,938)		(474,938)			$ 68,541
Debt securities
Realized and Unrealized Investment Gains Losses [Line Items]
Total change in unrealized investment (losses) gains	(100,490)	(10,627)	(297,065)	84,214
Previously impaired fixed maturity securities
Realized and Unrealized Investment Gains Losses [Line Items]
Total change in unrealized investment (losses) gains	(7)	61	4	905
Equity securities
Realized and Unrealized Investment Gains Losses [Line Items]
Total change in unrealized investment (losses) gains	0	(2,126)	0	(44,812)
Investment funds
Realized and Unrealized Investment Gains Losses [Line Items]
Total change in unrealized investment (losses) gains	$ 3,669	$ 4,129	$ (1,103)	$ 9,841
AOCI Including Portion Attributable to Noncontrolling Interest \| Accounting Standards Update 2016-01
Realized and Unrealized Investment Gains Losses [Line Items]
Increase (decrease) in accumulated other comprehensive income					$ (291,000)