Segment Information (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2016 USD ($) segment location	Mar. 31, 2015 USD ($)	Dec. 31, 2015 USD ($)
Segment Reporting [Abstract]
Number of business segments | segment	2
Segment Reporting Information [Line Items]
Net premiums earned	$ 241,298	$ 213,171
Investment income, net of investment expenses	22,224	24,363
Net realized investment gains (losses)	2,055	887
Other income	108	63
Total revenues	265,685	238,484
Net income	22,427	23,679
Assets	3,975,992	3,864,251	$ 3,890,376
Invested assets	$ 3,172,329	3,139,578	$ 3,142,760
Property and Casualty Insurance [Member]
Segment Reporting Information [Line Items]
Number of domestic locations | location	7
Total revenues	$ 231,334	210,645
Net income	22,020	23,103
Assets	2,344,686	2,166,432
Invested assets	1,675,088	1,562,710
Life Insurance [Member]
Segment Reporting Information [Line Items]
Total revenues	34,351	27,839
Net income	407	576
Assets	1,631,306	1,697,819
Invested assets	1,497,241	1,576,868
Operating Segments [Member]
Segment Reporting Information [Line Items]
Net premiums earned	241,298	213,365
Investment income, net of investment expenses	22,261	24,346
Net realized investment gains (losses)	2,055	887
Other income	108	63
Total revenues	265,722	238,661
Operating Segments [Member] | Property and Casualty Insurance [Member]
Segment Reporting Information [Line Items]
Net premiums earned	220,225	200,137
Investment income, net of investment expenses	9,409	10,730
Net realized investment gains (losses)	1,737	(239)
Other income	0	0
Total revenues	231,371	210,628
Operating Segments [Member] | Life Insurance [Member]
Segment Reporting Information [Line Items]
Net premiums earned	21,073	13,228
Investment income, net of investment expenses	12,852	13,616
Net realized investment gains (losses)	318	1,126
Other income	108	63
Total revenues	34,351	28,033
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Total revenues	(37)	(177)
Intersegment Eliminations [Member] | Property and Casualty Insurance [Member]
Segment Reporting Information [Line Items]
Total revenues	(37)	17
Intersegment Eliminations [Member] | Life Insurance [Member]
Segment Reporting Information [Line Items]
Total revenues	$ 0	$ (194)