Comprehensive Income (Loss) (Reclassification From Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other net realized capital gains (losses)	$ (268,966)	$ (137,346)
Other underwriting expenses	1,165	1,457
Income tax expense (benefit)	(245)	(306)
Net income (loss)	920	1,151
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)	35,364	(1,532)
Income tax expense (benefit)	(7,478)	516
Net income (loss)	27,886	(1,016)
Benefit Plan Net Gain (Loss) [Member] | Reclassification From Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other underwriting expenses	1,165	1,457
Income tax expense (benefit)	(245)	(306)
Net income (loss)	$ 920	$ 1,151