Segment Information (Income From Continuing Operations, Before Federal Income Tax) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Segment Reporting Information [Line Items]
Net investment income	$ 32,870	$ 32,628
Net realized investment gains	3,355	4,358
Total investment revenues	36,225	36,986
Total all segments	48,386	35,623
Interest expense	(5,831)	(4,700)
General corporate and other expenses	(13,687)	(7,732)
Income from continuing operations before federal income tax	28,868	23,191
Total standard Commercial Lines [Member]
Segment Reporting Information [Line Items]
Underwriting gain (loss), before federal income tax	6,102	409
Total standard Personal Lines [Member]
Segment Reporting Information [Line Items]
Underwriting gain (loss), before federal income tax	5,973	3,121
Total Standard Insurance Operations [Member]
Segment Reporting Information [Line Items]
Underwriting gain (loss), before federal income tax	12,075	3,530
GAAP combined ratio	96.90%	99.00%
Statutory combined ratio	96.80%	98.00%
Excess And Surplus Operations [Member]
Segment Reporting Information [Line Items]
Underwriting gain (loss), before federal income tax	$ 86	$ (4,893)
GAAP combined ratio	99.70%	150.30%
Statutory combined ratio	98.20%	120.30%