OPERATING SEGMENTS (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Summarized financial information for the company's segments
Total revenues	$ 1,618,711			$ 1,347,168			$ 4,451,516	$ 3,756,908
Pre-tax Adjusted Operating Income (Loss)	122,327			156,974			396,488	366,391
Realized gains (losses) on investments and derivatives	5,516			(20,255)			36,344	(39,102)
Income before income tax	127,843			136,719			432,832	327,289
Income tax expense	(27,217)			(26,619)			(85,811)	(61,582)
Net income	100,626	$ 108,111	$ 138,284	110,100	$ 81,495	$ 74,112	347,021	265,707
Adjusted operating income tax expense	(26,059)			(30,873)			(78,179)	(69,793)
After-tax adjusted operating income	96,268			126,101			318,309	296,598
Income tax (expense) benefit on adjustments	(1,158)			4,254			(7,632)	8,211
Realized investment gains (losses):
Derivative financial instruments	(102,403)			(27,465)			(370,123)	62,859
All other investments	88,409			(19,869)			317,501	(157,070)
Net impairment losses recognized in earnings	(10,818)			(14)			(14,658)	(3,664)
Less: related amortization	(6,205)			(5,859)			(37,406)	5,060
Less: VA GLWB economic cost	(24,123)			(21,234)			(66,218)	(63,833)
Operating Segment Assets
Investments and other assets	114,904,324						114,904,324		$ 85,476,658
DAC and VOBA	3,424,874						3,424,874		3,023,154
Other intangibles	596,336						596,336		613,431
Goodwill	825,511						825,511		825,511
Total assets	119,751,045						119,751,045		89,938,754
Life Marketing
Summarized financial information for the company's segments
Total revenues	472,649			438,585			1,371,548	1,288,455
Pre-tax Adjusted Operating Income (Loss)	(25,347)			2,521			(24,575)	(23,065)
Operating Segment Assets
Investments and other assets	15,780,011						15,780,011		14,575,702
DAC and VOBA	1,467,865						1,467,865		1,499,386
Other intangibles	248,475						248,475		262,758
Goodwill	215,254						215,254		215,254
Total assets	17,711,605						17,711,605		16,553,100
Acquisitions
Summarized financial information for the company's segments
Total revenues	859,524			581,054			2,136,497	1,469,787
Pre-tax Adjusted Operating Income (Loss)	103,210			93,648			247,932	208,206
Operating Segment Assets
Investments and other assets	52,877,466						52,877,466		31,859,520
DAC and VOBA	885,600						885,600		458,977
Other intangibles	37,287						37,287		31,975
Goodwill	23,862						23,862		23,862
Total assets	53,824,215						53,824,215		32,374,334
Annuities
Summarized financial information for the company's segments
Total revenues	92,565			129,280			332,189	413,170
Pre-tax Adjusted Operating Income (Loss)	35,860			45,587			135,347	142,052
Operating Segment Assets
Investments and other assets	21,500,280						21,500,280		20,199,597
DAC and VOBA	895,121						895,121		889,697
Other intangibles	161,509						161,509		156,785
Goodwill	343,247						343,247		343,247
Total assets	22,900,157						22,900,157		21,589,326
Stable Value Products
Summarized financial information for the company's segments
Total revenues	59,954			59,328			187,118	158,944
Pre-tax Adjusted Operating Income (Loss)	20,863			27,126			71,208	76,198
Operating Segment Assets
Investments and other assets	5,324,149						5,324,149		5,107,334
DAC and VOBA	6,019						6,019		6,121
Other intangibles	6,889						6,889		7,389
Goodwill	113,924						113,924		113,924
Total assets	5,450,981						5,450,981		5,234,768
Asset Protection
Summarized financial information for the company's segments
Total revenues	75,884			79,158			228,096	233,347
Pre-tax Adjusted Operating Income (Loss)	10,405			8,029			29,359	21,413
Operating Segment Assets
Investments and other assets	1,059,284						1,059,284		1,019,297
DAC and VOBA	170,269						170,269		168,973
Other intangibles	114,703						114,703		122,590
Goodwill	129,224						129,224		129,224
Total assets	1,473,480						1,473,480		1,440,084
Corporate and Other
Summarized financial information for the company's segments
Total revenues	58,135			59,763			196,068	193,205
Pre-tax Adjusted Operating Income (Loss)	(22,664)			$ (19,937)			(62,783)	$ (58,413)
Operating Segment Assets
Investments and other assets	18,363,134						18,363,134		12,715,208
DAC and VOBA	0						0		0
Other intangibles	27,473						27,473		31,934
Goodwill	0						0		0
Total assets	$ 18,390,607						$ 18,390,607		$ 12,747,142