Investments (Summary Of Net Realized Investment Gains And The Change In Net Unrealized Gains On Investments) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Gain (Loss) on Investments [Line Items]
Realized gains	$ 6,108	$ 18,850	$ 22,116	$ 47,266
Realized losses	(1,883)	(6,315)	(5,921)	(18,129)
Gains on securities measured at fair value through net income	13,402	4,706	22,297	9,283
Other-than-temporary impairment losses recognized in net income	(604)	(3,675)	(3,817)	(12,080)
Net realized investment gains	17,627	17,241	38,492	38,420
Change in net unrealized gains on investments included in other comprehensive income	283,918	255,844	507,490	592,691
Sales Of Fixed Maturities [Member]
Gain (Loss) on Investments [Line Items]
Realized gains	554	699	757	967
Realized losses	(412)	(142)	(602)	(555)
Sales Of Equity Securities [Member]
Gain (Loss) on Investments [Line Items]
Realized gains	1,295	17,798	16,533	45,526
Realized losses	(786)	(1,780)	(1,216)	(2,498)
Other [Member]
Gain (Loss) on Investments [Line Items]
Realized gains	4,259	353	4,826	773
Realized losses	(81)	(718)	(286)	(2,996)
Fixed Maturities [Member]
Gain (Loss) on Investments [Line Items]
Change in net unrealized gains on investments included in other comprehensive income	79,413	213,026	84,060	452,982
Equity Securities [Member]
Gain (Loss) on Investments [Line Items]
Change in net unrealized gains on investments included in other comprehensive income	204,372	42,786	423,424	139,744
Short-Term Investments [Member]
Gain (Loss) on Investments [Line Items]
Change in net unrealized gains on investments included in other comprehensive income	$ 133	$ 32	$ 6	$ (35)