Schedule IV Reinsurance (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Life insurance in force
Gross Amount	$ 17,564,270	$ 17,025,125	$ 16,504,539
Ceded to Other Companies	4,295,412	4,065,449	3,625,946
Assumed from Other Companies	0	0	0
Net Amount	$ 13,268,858	$ 12,959,676	$ 12,878,593
Percentage of Amount Assumed to Net	0.00%	0.00%	0.00%
Premiums
Gross Amount	$ 812,099	$ 777,651	$ 752,798
Ceded to Other Companies	22,036	22,826	25,077
Assumed from Other Companies	4,640	4,321	4,159
Net Amount	$ 794,703	$ 759,146	$ 731,880
Percentage of Amount Assumed to Net	0.60%	0.60%	0.60%
Property and Casualty
Premiums
Gross Amount	$ 658,960	$ 632,372	$ 610,347
Ceded to Other Companies	15,337	16,179	18,548
Assumed from Other Companies	4,640	4,321	4,159
Net Amount	$ 648,263	$ 620,514	$ 595,958
Percentage of Amount Assumed to Net	0.70%	0.70%	0.70%
Retirement
Premiums
Gross Amount	$ 28,003	$ 24,937	$ 25,378
Ceded to Other Companies	0	0	0
Assumed from Other Companies	0	0	0
Net Amount	$ 28,003	$ 24,937	$ 25,378
Percentage of Amount Assumed to Net	0.00%	0.00%	0.00%
Life
Premiums
Gross Amount	$ 125,136	$ 120,342	$ 117,073
Ceded to Other Companies	6,699	6,647	6,529
Assumed from Other Companies	0	0	0
Net Amount	$ 118,437	$ 113,695	$ 110,544
Percentage of Amount Assumed to Net	0.00%	0.00%	0.00%