REINSURANCE - Life Insurance In-Force and Effect of Reinsurance on Premiums Written and Earned (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Life insurance in-force
Direct life insurance in-force	$ 765,986,223	$ 751,512,468	$ 739,248,680
Amounts assumed from other companies	135,407,408	110,205,190	116,265,430
Amounts ceded to other companies	(302,149,614)	(328,377,398)	(348,994,650)
Net life insurance in-force	$ 599,244,017	$ 533,340,260	$ 506,519,460
Percentage of amount assumed to net	23.00%	21.00%	23.00%
Effect of reinsurance on premiums written and earned
Gross Amount	$ 3,036,853	$ 3,017,685	$ 2,929,767
Ceded to Other Companies	(1,384,941)	(1,360,735)	(1,314,716)
Assumed from Other Companies	643,992	459,734	478,164
Net Amount	2,295,904	2,116,684	2,093,215
Reinsurance receivables	4,700,000	5,100,000
Ceded benefits which are recoverable from reinsurers	115,800	96,600
Receivables related to insurance assumed	64,800	65,100
Life insurance
Effect of reinsurance on premiums written and earned
Gross Amount	2,681,191	2,655,846	2,610,682
Ceded to Other Companies	(1,173,194)	(1,151,175)	(1,126,915)
Assumed from Other Companies	626,283	435,113	454,999
Net Amount	2,134,280	1,939,784	1,938,766
Annuity policy fees	177,100	173,500	160,400
Accident/health insurance
Effect of reinsurance on premiums written and earned
Gross Amount	47,028	51,991	58,076
Ceded to Other Companies	(30,126)	(33,051)	(36,935)
Assumed from Other Companies	12,826	14,945	17,439
Net Amount	29,728	33,885	38,580
Property and liability insurance
Effect of reinsurance on premiums written and earned
Gross Amount	308,634	309,848	261,009
Ceded to Other Companies	(181,621)	(176,509)	(150,866)
Assumed from Other Companies	4,883	9,676	5,726
Net Amount	$ 131,896	$ 143,015	$ 115,869