Other Comprehensive Income (Loss) (Reclassifications From Accumulated Other Comprehensive Income (Loss) Into Income, By Component) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Reclassification Out Of Accumulated Other Comprehensive Income [Line Items]
Net realized investment gains (losses)	$ (67)	$ (7,642)	$ 614	$ (8,588)
Income Before Income Taxes	650,194	360,737	1,382,870	403,574
Underwriting, acquisition and insurance expenses	(462,316)	(451,570)	(917,528)	(875,960)
Income taxes	(143,711)	(81,150)	(298,874)	(189,581)
Net Income (Loss)	506,483	279,587	1,083,996	213,993
Reclassification Out Of Accumulated Other Comprehensive Income [Member] | Unrealized Holding Gains On Available-For-Sale Securities [Member]
Reclassification Out Of Accumulated Other Comprehensive Income [Line Items]
Net realized investment gains (losses)	(1,017)	7,457	(705)	6,426
Income taxes	214	(1,566)	148	(1,349)
Net Income (Loss)	(803)	5,891	(557)	5,077
Reclassification Out Of Accumulated Other Comprehensive Income [Member] | Net Actuarial Pension Loss [Member]
Reclassification Out Of Accumulated Other Comprehensive Income [Line Items]
Underwriting, acquisition and insurance expenses	(652)	(760)	(2,375)	(1,560)
Income taxes	137	192	499	328
Net Income (Loss)	$ (515)	$ (568)	$ (1,876)	$ (1,232)