INCOME TAXES - Effective Income Tax Rate and Components of Income Tax and Deferred Liability (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Effective income tax rate related to continuing operations
Statutory federal income tax rate applied to pre-tax income	21.00%	21.00%	21.00%
State income taxes	(0.30%)	0.40%	4.20%
Investment income not subject to tax	(2.50%)	(1.60%)	(4.50%)
Prior period adjustments	(0.40%)	0.10%	1.60%
Other	(0.60%)	(0.80%)	(0.60%)
Effective income tax rate	17.20%	19.10%	21.70%
Current income tax expense (benefit):
Federal	$ 113,821	$ 381,202	$ 113,925
State	(4,965)	9,112	9,699
Total current	108,856	390,314	123,624
Deferred income tax expense (benefit):
Federal	(41,270)	(254,184)	(73,364)
State	3,576	(5,666)	3,401
Total deferred	(37,694)	(259,850)	(69,963)
Deferred income tax assets:
Loss and credit carryforwards	124,024	132,295
Deferred compensation	53,797	55,559
Deferred policy acquisition costs	141,946	217,967
Premium on non-recourse funding obligations	236	784
Valuation allowance	(9,073)	(9,153)
Deferred income tax assets	310,930	397,452
Deferred income tax liabilities:
Premium receivables and policy liabilities	227,560	211,458
VOBA and other intangibles	581,993	596,756
Invested assets (other than unrealized gains (losses))	370,418	557,763
Net unrealized gains on investments	941,972	376,288
Other	53,167	27,157
Deferred income tax liabilities	2,175,110	1,769,422
Net deferred income tax liability	(1,864,180)	(1,371,970)
Reconciliation of the beginning and ending amount of unrecognized tax benefits
Balance, beginning of period	1,791	7,134	11,353
Additions for tax positions of the current year	0	0	0
Additions for tax positions of prior years	0	0	0
Reductions of tax positions of prior years:
Changes in judgment	0	0	(4,219)
Settlements during the period	0	(5,343)	0
Lapses of applicable statute of limitations	0	0	0
Balance, end of period	$ 1,791	$ 1,791	$ 7,134