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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		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Jan. 01, 2018	Dec. 31, 2017
Realized and Unrealized Investment Gains Losses [Line Items]
Total change in unrealized investment gains	$ (40,488)	$ 68,282	$ (201,336)	$ 58,711
Income tax benefit (expense)	8,118	(24,713)	43,194	(23,973)
Noncontrolling interests	37	(5)	26	14
Total change in unrealized gains	(32,333)	43,564	(158,116)	34,752
Increase (decrease) in accumulated other comprehensive income	(395,842)		(395,842)			$ 68,541
Debt securities
Realized and Unrealized Investment Gains Losses [Line Items]
Total change in unrealized investment gains	(36,848)	56,857	(196,575)	94,841
Previously impaired fixed maturity securities
Realized and Unrealized Investment Gains Losses [Line Items]
Total change in unrealized investment gains	(2)	743	11	844
Equity securities
Realized and Unrealized Investment Gains Losses [Line Items]
Total change in unrealized investment gains	0	6,176	0	(42,686)
Investment funds
Realized and Unrealized Investment Gains Losses [Line Items]
Total change in unrealized investment gains	$ (3,638)	$ 4,506	$ (4,772)	$ 5,712
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)