Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Summarized financial information for these segments
Insurance premiums and contract charges earned	$ 173,761	$ 167,904	$ 514,480	$ 499,743
Net investment income	78,466	76,649	233,230	228,658
Net income (loss)	23,599	32,266	76,606	72,040
Assets	8,522,731		8,522,731		8,167,726
Property and casualty [Member]
Summarized financial information for these segments
Insurance premiums and contract charges earned	140,812	136,809	418,205	407,471
Net investment income	8,824	9,022	26,894	27,250
Net income (loss)	11,037	13,529	25,363	22,633
Assets	1,005,190		1,005,190		1,016,368
Annuity [Member]
Summarized financial information for these segments
Insurance premiums and contract charges earned	5,895	5,551	16,714	16,053
Net investment income	52,175	50,742	154,818	150,000
Net income (loss)	11,605	9,918	31,896	29,380
Assets	5,724,170		5,724,170		5,380,780
Life [Member]
Summarized financial information for these segments
Insurance premiums and contract charges earned	27,054	25,544	79,561	76,219
Net investment income	17,703	17,131	52,232	52,148
Net income (loss)	5,884	4,941	15,752	16,236
Assets	1,698,730		1,698,730		1,663,696
Corporate and other [Member]
Summarized financial information for these segments
Net investment income	2	0	6	1
Net income (loss)	(4,927)	3,878	3,595	3,791
Assets	130,911		130,911		131,449
Intersegment eliminations [Member]
Summarized financial information for these segments
Net investment income	(238)	(246)	(720)	(741)
Assets	$ (36,270)		$ (36,270)		$ (24,567)