Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Summarized financial information for these segments
Insurance premiums and contract charges earned	$ 171,561	$ 166,335	$ 340,719	$ 331,839
Net investment income	77,361	76,334	154,764	152,009
Net income (loss)	25,995	13,103	53,007	39,774
Assets	8,355,778		8,355,778		8,167,726
Property and casualty [Member]
Summarized financial information for these segments
Insurance premiums and contract charges earned	139,457	135,616	277,393	270,662
Net investment income	9,100	9,356	18,070	18,228
Net income (loss)	4,166	(4,127)	14,326	9,104
Assets	999,000		999,000		1,016,368
Annuity [Member]
Summarized financial information for these segments
Insurance premiums and contract charges earned	5,747	5,537	10,819	10,502
Net investment income	51,289	49,718	102,643	99,258
Net income (loss)	9,230	7,874	20,291	19,462
Assets	5,570,880		5,570,880		5,380,780
Life [Member]
Summarized financial information for these segments
Insurance premiums and contract charges earned	26,357	25,182	52,507	50,675
Net investment income	17,210	17,505	34,529	35,017
Net income (loss)	5,528	6,130	9,868	11,295
Assets	1,683,678		1,683,678		1,663,696
Corporate and other [Member]
Summarized financial information for these segments
Net investment income	4	1	4	1
Net income (loss)	7,071	3,226	8,522	(87)
Assets	130,737		130,737		131,449
Intersegment eliminations [Member]
Summarized financial information for these segments
Net investment income	(242)	(246)	(482)	(495)
Assets	$ (28,517)		$ (28,517)		$ (24,567)