OPERATING SEGMENTS (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Summarized financial information for the company's segments
Total revenues	$ 1,418,775		$ 1,243,908		$ 2,832,805	$ 2,409,740
Pre-tax Adjusted Operating Income (Loss)	131,491		116,596		274,161	209,417
Realized (losses) gains on investments and derivatives	(1,417)		(17,824)		30,828	(18,847)
Income before income tax	130,074		98,772		304,989	190,570
Income tax expense	(21,963)		(17,277)		(58,594)	(34,963)
Net income	108,111	$ 138,284	81,495	$ 74,112	246,395	155,607
Adjusted operating income tax (expense) benefit	(22,261)		(20,877)		(52,120)	(38,920)
After-tax adjusted operating income	109,230		95,719		222,041	170,497
Income tax benefit (expense) on adjustments	298		3,600		(6,474)	3,957
Realized investment (losses) gains:
Derivative financial instruments	(148,049)		12,265		(267,720)	90,324
All other investments	99,502		(49,602)		229,092	(137,201)
Net impairment losses recognized in earnings	(698)		(5)		(3,840)	(3,650)
Less: related amortization	(26,840)		1,763		(31,201)	10,919
Less: VA GLWB economic cost	(20,988)		(21,281)		(42,095)	(42,599)
Operating Segment Assets
Investments and other assets	112,528,973				112,528,973		$ 85,476,658
DAC and VOBA	3,474,557				3,474,557		3,023,154
Other intangibles	616,931				616,931		613,431
Goodwill	825,511				825,511		825,511
Total assets	117,445,972				117,445,972		89,938,754
Life Marketing
Summarized financial information for the company's segments
Total revenues	441,559		414,954		898,899	849,870
Pre-tax Adjusted Operating Income (Loss)	(462)		(7,737)		772	(25,586)
Operating Segment Assets
Investments and other assets	15,433,940				15,433,940		14,575,702
DAC and VOBA	1,494,118				1,494,118		1,499,386
Other intangibles	253,243				253,243		262,758
Goodwill	215,254				215,254		215,254
Total assets	17,396,555				17,396,555		16,553,100
Acquisitions
Summarized financial information for the company's segments
Total revenues	667,031		509,639		1,276,973	888,733
Pre-tax Adjusted Operating Income (Loss)	69,810		59,038		144,722	114,558
Operating Segment Assets
Investments and other assets	52,753,065				52,753,065		31,859,520
DAC and VOBA	914,610				914,610		458,977
Other intangibles	38,291				38,291		31,975
Goodwill	23,862				23,862		23,862
Total assets	53,729,828				53,729,828		32,374,334
Annuities
Summarized financial information for the company's segments
Total revenues	100,407		133,177		239,624	283,890
Pre-tax Adjusted Operating Income (Loss)	45,271		55,934		99,487	96,465
Operating Segment Assets
Investments and other assets	21,206,967				21,206,967		20,199,597
DAC and VOBA	890,214				890,214		889,697
Other intangibles	172,420				172,420		156,785
Goodwill	343,247				343,247		343,247
Total assets	22,612,848				22,612,848		21,589,326
Stable Value Products
Summarized financial information for the company's segments
Total revenues	67,585		45,748		127,164	99,616
Pre-tax Adjusted Operating Income (Loss)	28,106		19,992		50,345	49,072
Operating Segment Assets
Investments and other assets	5,688,707				5,688,707		5,107,334
DAC and VOBA	6,877				6,877		6,121
Other intangibles	7,056				7,056		7,389
Goodwill	113,924				113,924		113,924
Total assets	5,816,564				5,816,564		5,234,768
Asset Protection
Summarized financial information for the company's segments
Total revenues	76,014		77,814		152,212	154,189
Pre-tax Adjusted Operating Income (Loss)	9,211		7,166		18,954	13,384
Operating Segment Assets
Investments and other assets	1,055,887				1,055,887		1,019,297
DAC and VOBA	168,738				168,738		168,973
Other intangibles	117,374				117,374		122,590
Goodwill	129,224				129,224		129,224
Total assets	1,471,223				1,471,223		1,440,084
Corporate and Other
Summarized financial information for the company's segments
Total revenues	66,179		62,576		137,933	133,442
Pre-tax Adjusted Operating Income (Loss)	(20,445)		$ (17,797)		(40,119)	$ (38,476)
Operating Segment Assets
Investments and other assets	16,390,407				16,390,407		12,715,208
DAC and VOBA	0				0		0
Other intangibles	28,547				28,547		31,934
Goodwill	0				0		0
Total assets	$ 16,418,954				$ 16,418,954		$ 12,747,142