Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Summarized financial information for these segments
Insurance premiums and contract charges earned	$ 182,812	$ 179,030	$ 544,927	$ 533,571
Net investment income	81,016	82,591	248,324	247,040
Net income (loss)	21,984	25,357	72,442	74,175
Assets	9,903,499		9,903,499		$ 9,768,527
Property and casualty [Member]
Summarized financial information for these segments
Insurance premiums and contract charges earned	149,210	145,520	443,616	434,070
Net investment income	7,350	8,877	25,790	27,617
Net income (loss)	11,253	11,769	32,120	30,691
Assets	1,103,258		1,103,258		1,107,962
Annuity [Member]
Summarized financial information for these segments
Insurance premiums and contract charges earned	6,541	6,654	19,280	19,031
Net investment income	56,271	56,026	169,846	166,221
Net income (loss)	8,716	10,264	32,973	34,076
Assets	6,778,398		6,778,398		6,683,473
Life [Member]
Summarized financial information for these segments
Insurance premiums and contract charges earned	27,061	26,856	82,031	80,470
Net investment income	17,612	17,915	53,342	53,891
Net income (loss)	3,619	3,916	10,647	12,813
Assets	1,913,404		1,913,404		1,858,150
Corporate and other [Member]
Summarized financial information for these segments
Net investment income	5	3	17	7
Net income (loss)	(1,604)	(592)	(3,298)	(3,405)
Assets	141,723		141,723		155,678
Intersegment eliminations [Member]
Summarized financial information for these segments
Net investment income	(222)	$ (230)	(671)	$ (696)
Assets	$ (33,284)		$ (33,284)		$ (36,736)