Accumulated Other Comprehensive Income (Reclassification Out Of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net realized gains on investments, excluding other-than-temporary impairment losses										$ 36,850	$ 60,813	$ 38,912
Portion of net loss recognized in other comprehensive income, before taxes										(2,188)	(39)	(129)
Provision for income taxes										(59,626)	(273,230)	(300,792)
Net income		$ 65,744	$ (7,022)	$ 32,789	$ 50,044	$ 49,755	$ 140,297	$ 143,610	$ 137,245	141,555	470,907	488,907
Total pre-tax income										201,181	744,137	789,699
Reclassification out of Accumulated other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income										36,615	40,849	45,228
Accumulated Net Unrealized Investment Gain (Loss) | Reclassification out of Accumulated other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net realized gains on investments, excluding other-than-temporary impairment losses										41,992	49,248	35,454
Provision for income taxes										(14,697)	(17,237)	(12,409)
Net income										27,295	32,011	23,045
Accumulated Other-than-Temporary Impairment | Reclassification out of Accumulated other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Portion of net loss recognized in other comprehensive income, before taxes										(2,176)	2,289	7,389
Provision for income taxes										762	(801)	(2,586)
Net income										(1,414)	1,488	4,803
Accumulated Defined Benefit Plans Adjustment | Reclassification out of Accumulated other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Provision for income taxes										(5,780)	(3,958)	(9,359)
Net income										10,734	7,350	17,380
Amortization of prior service cost	[1]									(146)	(97)	(77)
Amortization of net loss	[1]									16,660	11,405	26,816
Total pre-tax income										$ 16,514	$ 11,308	$ 26,739

[1] These accumulated other comprehensive income components are included in the computation of net periodic pension cost. See Note 21 - Retirement and Other Employee Benefits for additional information