INCOME TAXES - Effective Income Tax Rate and Components of Income Tax and Deferred Liability (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Effective income tax rate related to continuing operations
Statutory federal income tax rate applied to pre-tax income	21.00%	35.00%	35.00%
State income taxes	4.90%	0.60%	0.80%
Investment income not subject to tax	(2.90%)	(5.00%)	(2.70%)
Prior period adjustments	(2.80%)	0.00%	0.00%
Federal Tax law changes	0.00%	(183.30%)	0.00%
Other	0.90%	(1.60%)	0.70%
Effective tax rate (as a percent)	21.10%	(154.30%)	33.80%
Current income tax expense:
Federal	$ 87,276	$ 21,853	$ (50,638)
State	8,285	4,399	3,919
Total current	95,561	26,252	(46,719)
Deferred income tax expense:
Federal	(30,629)	(693,860)	240,127
State	15,725	(3,867)	7,560
Total deferred	(14,904)	(697,727)	$ 247,687
Deferred income tax assets:
Loss and credit carryforwards	46,236	209,401
Deferred compensation	126,398	138,945
Deferred policy acquisition costs	116,044	23,876
Premium on corporate debt	46,154	57,402
Net unrealized loss on investments	374,905	0
Other	25,691	28,179
Valuation allowance	(5,079)	(3,951)
Deferred income tax assets	730,349	453,852
Deferred income tax liabilities:
Premium receivables and policy liabilities	408,502	573,469
VOBA and other intangibles	478,526	433,321
Invested assets (other than unrealized gains (losses))	682,637	672,549
Net unrealized gains on investments	0	6,920
Deferred income tax liabilities	1,569,665	1,686,259
Net deferred income tax liability	(839,316)	(1,232,407)
Provisional income tax benefit		797,600
Increase in income tax expense	10,700
State based operating loss carryforwards, valuation allowance	6,400	$ 5,000
Change in valuation allowance, before federal income taxes	1,400
State net operating loss carryforwards	19,700
2036
Deferred income tax liabilities:
Net operating loss carryforwards	$ 135,400