Segment Information (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016 USD ($) location	Jun. 30, 2015 USD ($)	Jun. 30, 2016 USD ($) segment location	Jun. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)
Segment Reporting [Abstract]
Number of business segments | segment			2
Segment Reporting Information [Line Items]
Net premiums earned	$ 253,487	$ 229,225	$ 494,785	$ 442,396
Investment income, net of investment expenses	24,507	25,792	46,731	50,155
Net realized investment gains (losses)	1,596	769	3,651	1,656
Other income	183	132	291	195
Total revenues	279,773	255,918	545,458	494,402
Net income	3,114	15,018	25,541	38,697
Assets	4,105,838	3,891,483	4,105,838	3,891,483	$ 3,890,376
Invested assets	$ 3,271,406	3,136,866	$ 3,271,406	3,136,866	$ 3,142,760
Property and Casualty Insurance [Member]
Segment Reporting Information [Line Items]
Number of domestic locations | location	7		7
Total revenues	$ 244,866	221,208	$ 476,200	431,853
Net income	3,434	13,297	25,454	36,400
Assets	2,459,526	2,216,690	2,459,526	2,216,690
Invested assets	1,723,641	1,581,176	1,723,641	1,581,176
Life Insurance [Member]
Segment Reporting Information [Line Items]
Total revenues	34,907	34,710	69,258	62,549
Net income	(320)	1,721	87	2,297
Assets	1,646,312	1,674,793	1,646,312	1,674,793
Invested assets	1,547,765	1,555,690	1,547,765	1,555,690
Operating Segments [Member]
Segment Reporting Information [Line Items]
Net premiums earned	253,487	229,420	494,785	442,785
Investment income, net of investment expenses	24,544	25,812	46,805	50,158
Net realized investment gains (losses)	1,596	769	3,651	1,656
Other income	183	132	291	195
Total revenues	279,810	256,133	545,532	494,794
Operating Segments [Member] | Property and Casualty Insurance [Member]
Segment Reporting Information [Line Items]
Net premiums earned	232,282	209,266	452,507	409,403
Investment income, net of investment expenses	11,655	12,139	21,064	22,869
Net realized investment gains (losses)	966	(177)	2,703	(416)
Other income	0	0	0	0
Total revenues	244,903	221,228	476,274	431,856
Operating Segments [Member] | Life Insurance [Member]
Segment Reporting Information [Line Items]
Net premiums earned	21,205	20,154	42,278	33,382
Investment income, net of investment expenses	12,889	13,673	25,741	27,289
Net realized investment gains (losses)	630	946	948	2,072
Other income	183	132	291	195
Total revenues	34,907	34,905	69,258	62,938
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Total revenues	(37)	(215)	(74)	(392)
Intersegment Eliminations [Member] | Property and Casualty Insurance [Member]
Segment Reporting Information [Line Items]
Total revenues	(37)	(20)	(74)	(3)
Intersegment Eliminations [Member] | Life Insurance [Member]
Segment Reporting Information [Line Items]
Total revenues	$ 0	$ (195)	$ 0	$ (389)