Schedule II Condensed Financial Information of Registrant (Details 1) - USD ($) $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	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, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenues
Net investment income													$ 361,186	$ 332,600	$ 329,815
Realized investment gains													4,123	12,713	10,917
Total revenues	$ 282,873	$ 291,176	$ 283,558	$ 271,303	$ 276,106	$ 265,753	$ 268,470	$ 270,119	$ 269,157	$ 265,520	$ 264,743	$ 261,265	1,128,910	1,080,448	1,060,685
Expenses
Interest													11,808	13,122	14,198
Debt retirement costs													0	2,338	0
Total expenses													1,014,678	950,996	914,572
Income tax benefit													30,467	35,970	41,870
Net income	$ 19,823	$ 26,923	$ 11,866	$ 25,153	$ 21,040	$ 21,984	$ 16,183	$ 34,275	$ 30,068	$ 25,357	$ 20,452	$ 28,366	83,765	93,482	104,243
Parent Company [Member]
Revenues
Net investment income													20	33	10
Realized investment gains													0	0	0
Total revenues													20	33	10
Expenses
Interest													11,808	13,122	14,198
Debt retirement costs													0	2,338	0
Other													5,631	5,153	5,071
Total expenses													17,439	20,613	19,269
Loss before income tax benefit and equity in net earnings of subsidiaries													(17,419)	(20,580)	(19,259)
Income tax benefit													(6,076)	(7,202)	(6,734)
Loss before equity in net earnings of subsidiaries													(11,343)	(13,378)	(12,525)
Equity in net earnings of subsidiaries													95,108	106,860	116,768
Net income													$ 83,765	$ 93,482	$ 104,243