Other Comprehensive Income (Reclassifications From Accumulated Other Comprehensive Income Into Income, By Component) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Reclassification Out Of Accumulated Other Comprehensive Income [Line Items]
Other-than-temporary impairment losses recognized in net income	$ (604)	$ (3,675)	$ (3,817)	$ (12,080)
Net realized investment gains, excluding other-than-temporary impairment losses	18,231	20,916	42,309	50,500
Income Before Income Taxes	209,545	115,891	303,589	330,227
Underwriting, acquisition and insurance expenses	(400,035)	(375,580)	(773,266)	(740,268)
Income taxes	(58,118)	(35,218)	(81,122)	(85,908)
Net Income	151,427	80,673	222,467	244,319
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]
Other-than-temporary impairment losses recognized in net income	(604)	(3,675)	(3,817)	(12,080)
Net realized investment gains, excluding other-than-temporary impairment losses	690	16,575	15,604	43,440
Income Before Income Taxes	86	12,900	11,787	31,360
Income taxes	136	(2,333)	(2,396)	(7,810)
Net Income	222	10,567	9,391	23,550
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	(1,056)	(480)	(1,951)	(1,045)
Income taxes	154	86	333	188
Net Income	$ (902)	$ (394)	$ (1,618)	$ (857)