Schedule II Condensed Financial Information of Registrant (Details 1) - USD ($) $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenues
Net investment income													$ 332,600	$ 329,815	$ 313,610
Realized investment gains													12,713	10,917	22,245
Total revenues	$ 276,106	$ 265,753	$ 268,470	$ 270,119	$ 269,157	$ 265,520	$ 264,743	$ 261,265	$ 259,215	$ 251,884	$ 265,637	$ 254,531	1,080,448	1,060,685	1,031,267
Expenses
Interest													13,122	14,198	14,236
Debt retirement costs													2,338	0	0
Total expenses													950,996	914,572	877,201
Income tax benefit													35,970	41,870	43,173
Net income	$ 21,040	$ 21,984	$ 16,183	$ 34,275	$ 30,068	$ 25,357	$ 20,452	$ 28,366	$ 34,287	$ 23,599	$ 25,995	$ 27,012	93,482	104,243	110,893
Parent Company [Member]
Revenues
Net investment income													33	10	6
Realized investment gains													0	0	208
Total revenues													33	10	214
Expenses
Interest													13,122	14,198	14,236
Debt retirement costs													2,338	0	0
Other													5,153	5,071	4,832
Total expenses													20,613	19,269	19,068
Loss before income tax benefit and equity in net earnings of subsidiaries													(20,580)	(19,259)	(18,854)
Income tax benefit													(7,202)	(6,734)	(6,599)
Loss before equity in net earnings of subsidiaries													(13,378)	(12,525)	(12,255)
Equity in net earnings of subsidiaries													106,860	116,768	123,148
Net income													$ 93,482	$ 104,243	$ 110,893