Comprehensive Income (Loss) (Reclassification From Accumulated Other Comprehensive Income) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other net realized capital gains (losses)									$ 245,591	$ 723,149	$ 398,336
Other underwriting expenses									(192,032)	(193,499)	(170,604)
Income tax expense (benefit)									(203,562)	(407,238)	(172,995)
NET INCOME (LOSS)	109,345	100,141	158,174	86,466	183,597	243,753	85,262	285,651	454,126	798,263	520,329
URA(D) On Securities [Member] | Reclassification From Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other net realized capital gains (losses)									41,624	(3,792)
Income tax expense (benefit)									(14,551)	1,327
NET INCOME (LOSS)									27,073	(2,465)
Benefit Plan Liability [Member] | Reclassification From Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other underwriting expenses									4,647	8,889
Income tax expense (benefit)									(1,627)	(3,111)
NET INCOME (LOSS)									$ 3,020	$ 5,778