Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Summarized financial information for these segments
Insurance premiums and contract charges earned	$ 179,030	$ 173,761	$ 533,571	$ 514,480
Net investment income	82,591	78,466	247,040	233,230
Net income (loss)	25,357	23,599	74,175	76,606
Assets	9,642,964		9,642,964		8,826,672
Property and casualty [Member]
Summarized financial information for these segments
Insurance premiums and contract charges earned	145,520	140,812	434,070	418,205
Net investment income	8,877	8,824	27,617	26,894
Net income (loss)	11,769	11,037	30,691	25,363
Assets	1,079,649		1,079,649		1,001,561
Annuity [Member]
Summarized financial information for these segments
Insurance premiums and contract charges earned	6,654	5,895	19,031	16,714
Net investment income	56,026	52,175	166,221	154,818
Net income (loss)	10,264	11,605	34,076	31,896
Assets	6,496,985		6,496,985		5,963,348
Life [Member]
Summarized financial information for these segments
Insurance premiums and contract charges earned	26,856	27,054	80,470	79,561
Net investment income	17,915	17,703	53,891	52,232
Net income (loss)	3,916	5,884	12,813	15,752
Assets	1,941,982		1,941,982		1,743,084
Corporate and other [Member]
Summarized financial information for these segments
Net investment income	3	2	7	6
Net income (loss)	(592)	(4,927)	(3,405)	3,595
Assets	156,124		156,124		154,557
Intersegment eliminations [Member]
Summarized financial information for these segments
Net investment income	(230)	(238)	(696)	(720)
Assets	$ (31,776)		$ (31,776)		$ (35,878)