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Segment Information (Reconciliation of Segment Results to Income from Continuing Operations, before Federal Income Tax) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total investment revenues	$ 173,347	$ 344,188	$ 222,890
Interest expense	(28,847)	(29,165)	(30,839)
Corporate expenses	(31,116)	(28,305)	(25,412)
Income before federal income tax	280,186	505,310	302,988
Preferred stock dividends	(9,200)	(9,353)	0
Income available to common stockholders, before federal income tax	270,986	495,957	302,988
Standard Commercial Lines [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Underwriting income (loss), before federal income tax	143,696	198,596	151,731
Standard Personal Lines
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Underwriting income (loss), before federal income tax	(7,193)	3,966	(15,508)
E&S Lines [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Underwriting income (loss), before federal income tax	30,299	16,030	126
Operating Segments [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total all segments	$ 340,149	$ 562,780	$ 359,239

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