Other Comprehensive Income (Loss) (Schedule Of Tax Expense (Benefit) Of Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Other Comprehensive Income (Loss), Tax [Abstract]
Net holding gains (losses) arising during the period	$ 84,219	$ (68,056)	$ 372,469
Reclassification adjustments for net gains (losses) included in net income (loss)	(305)	2,086	(10,072)
Change in net unrealized gains on investments	83,914	(65,970)	362,397
Change in foreign currency translation adjustments	0	1,523	28
Change in net actuarial pension loss	1,348	622	1,284
Total	$ 85,262	$ (63,825)	$ 363,709