OPERATING SEGMENTS (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Summarized financial information for the company's segments
Revenues	$ 1,284,046	$ 1,347,168	$ 1,243,908	$ 1,165,832	$ 1,142,040	$ 1,084,388	$ 1,087,067	$ 1,105,297	$ 5,040,954	$ 4,418,792	$ 4,483,947
Pre-tax Adjusted Operating Income (Loss)									478,535	506,892	503,369
Realized gains (losses) on investments and derivatives									(95,517)	(71,835)	90,628
Income before income tax	55,729	136,719	98,772	91,798	86,090	110,850	125,768	112,349	383,018	435,057	593,997
Income tax expense (benefit)	(19,075)	(26,619)	(17,277)	(17,686)	778,218	(28,308)	(41,500)	(36,935)	(80,657)	671,475	(200,968)
Net income	36,654	110,100	81,495	74,112	864,308	82,542	84,268	75,414	302,361	1,106,532	393,029
Adjusted operating income tax (expense) benefit									(100,716)	646,333	(169,247)
After-tax adjusted operating income									377,819	1,153,225	334,122
Income tax benefit (expense) on adjustments									20,059	25,142	(31,721)
Realized investment (losses) gains:
Derivative financial instruments									60,988	(305,828)	(40,288)
Realized gains (losses) on investments and derivatives									(223,649)	121,428	90,659
Net impairment losses recognized in earnings	(26,060)	(14)	(5)	(3,645)	(853)	(273)	(2,785)	(7,831)	(29,724)	(11,742)	(17,748)
Less: related amortization									(11,856)	(39,480)	24,360
Less: VA GLWB economic cost									(85,012)	(84,827)	(82,365)
Net investment income	674,286	$ 672,139	$ 616,462	$ 520,863	529,490	$ 507,914	$ 507,771	$ 506,413	2,483,750	2,051,588	1,942,456
Amortization of deferred policy acquisition costs and value of business acquired									225,808	78,221	149,064
Operating Segment Assets
Investments and other assets	85,476,658				75,973,148				85,476,658	75,973,148
Deferred policy acquisition costs and value of business acquired	3,023,154				2,199,577				3,023,154	2,199,577	2,019,829
Other intangibles	613,431				663,572				613,431	663,572
Goodwill	825,511				793,470				825,511	793,470
Total assets	89,938,754				79,629,767				89,938,754	79,629,767
Life Marketing
Realized investment (losses) gains:
Amortization of deferred policy acquisition costs and value of business acquired									116,917	120,753	130,708
Operating Segment Assets
Deferred policy acquisition costs and value of business acquired	1,499,386				1,320,776				1,499,386	1,320,776	1,218,944
Acquisitions
Realized investment (losses) gains:
Amortization of deferred policy acquisition costs and value of business acquired									18,690	(6,939)	8,178
Operating Segment Assets
Deferred policy acquisition costs and value of business acquired	458,976				74,862				458,976	74,862	106,532
Annuities
Realized investment (losses) gains:
Amortization of deferred policy acquisition costs and value of business acquired									24,274	(54,471)	(11,031)
Operating Segment Assets
Deferred policy acquisition costs and value of business acquired	889,697				772,633				889,697	772,633	655,618
Stable Value Products
Realized investment (losses) gains:
Amortization of deferred policy acquisition costs and value of business acquired									3,201	2,354	1,176
Operating Segment Assets
Deferred policy acquisition costs and value of business acquired	6,121				6,864				6,121	6,864	5,455
Asset Protection
Realized investment (losses) gains:
Amortization of deferred policy acquisition costs and value of business acquired									62,726	16,524	20,033
Operating Segment Assets
Deferred policy acquisition costs and value of business acquired	168,974				24,442				168,974	24,442	33,280
Corporate and Other
Realized investment (losses) gains:
Amortization of deferred policy acquisition costs and value of business acquired									0	0	0
Operating Segment Assets
Deferred policy acquisition costs and value of business acquired	0				0				0	0	0
Operating
Summarized financial information for the company's segments
Revenues									5,040,954	4,418,792	4,483,947
Pre-tax Adjusted Operating Income (Loss)									478,535	506,892	503,369
Realized investment (losses) gains:
Net investment income									2,483,750	2,051,588	1,942,456
Amortization of deferred policy acquisition costs and value of business acquired									225,808	78,221	149,064
Operating | Life Marketing
Summarized financial information for the company's segments
Revenues									1,689,795	1,667,118	1,627,848
Pre-tax Adjusted Operating Income (Loss)									(19,376)	50,778	39,745
Realized investment (losses) gains:
Net investment income									551,781	553,999	525,495
Amortization of deferred policy acquisition costs and value of business acquired									116,917	120,753	130,708
Operating Segment Assets
Investments and other assets	14,575,702				14,914,418				14,575,702	14,914,418
Deferred policy acquisition costs and value of business acquired	1,499,386				1,320,776				1,499,386	1,320,776
Other intangibles	262,758				282,361				262,758	282,361
Goodwill	215,254				200,274				215,254	200,274
Total assets	16,553,100				16,717,829				16,553,100	16,717,829
Operating | Acquisitions
Summarized financial information for the company's segments
Revenues									2,027,195	1,569,083	1,676,017
Pre-tax Adjusted Operating Income (Loss)									282,715	249,749	260,511
Realized investment (losses) gains:
Net investment income									1,108,218	752,520	764,571
Amortization of deferred policy acquisition costs and value of business acquired									18,690	(6,939)	8,178
Operating Segment Assets
Investments and other assets	31,859,520				19,588,133				31,859,520	19,588,133
Deferred policy acquisition costs and value of business acquired	458,977				74,862				458,977	74,862
Other intangibles	31,975				34,548				31,975	34,548
Goodwill	23,862				14,524				23,862	14,524
Total assets	32,374,334				19,712,067				32,374,334	19,712,067
Operating | Annuities
Summarized financial information for the company's segments
Revenues									545,922	450,306	574,934
Pre-tax Adjusted Operating Income (Loss)									167,186	213,080	213,293
Realized investment (losses) gains:
Net investment income									340,685	321,844	322,608
Amortization of deferred policy acquisition costs and value of business acquired									24,274	(54,471)	(11,031)
Operating Segment Assets
Investments and other assets	20,199,597				20,938,409				20,199,597	20,938,409
Deferred policy acquisition costs and value of business acquired	889,697				772,634				889,697	772,634
Other intangibles	156,785				170,117				156,785	170,117
Goodwill	343,247				336,677				343,247	336,677
Total assets	21,589,326				22,217,837				21,589,326	22,217,837
Operating | Stable Value Products
Summarized financial information for the company's segments
Revenues									219,501	190,006	114,580
Pre-tax Adjusted Operating Income (Loss)									102,328	105,261	61,294
Realized investment (losses) gains:
Net investment income									217,778	186,576	107,010
Amortization of deferred policy acquisition costs and value of business acquired									3,201	2,354	1,176
Operating Segment Assets
Investments and other assets	5,107,334				4,569,639				5,107,334	4,569,639
Deferred policy acquisition costs and value of business acquired	6,121				6,864				6,121	6,864
Other intangibles	7,389				8,056				7,389	8,056
Goodwill	113,924				113,813				113,924	113,813
Total assets	5,234,768				4,698,372				5,234,768	4,698,372
Operating | Asset Protection
Summarized financial information for the company's segments
Revenues									310,243	327,573	269,145
Pre-tax Adjusted Operating Income (Loss)									29,911	24,356	16,487
Realized investment (losses) gains:
Net investment income									30,457	27,325	22,082
Amortization of deferred policy acquisition costs and value of business acquired									62,726	16,524	20,033
Operating Segment Assets
Investments and other assets	1,019,297				918,952				1,019,297	918,952
Deferred policy acquisition costs and value of business acquired	168,973				24,441				168,973	24,441
Other intangibles	122,590				133,234				122,590	133,234
Goodwill	129,224				128,182				129,224	128,182
Total assets	1,440,084				1,204,809				1,440,084	1,204,809
Operating | Corporate and Other
Summarized financial information for the company's segments
Revenues									248,298	214,706	221,423
Pre-tax Adjusted Operating Income (Loss)									(84,229)	(136,332)	(87,961)
Realized investment (losses) gains:
Net investment income									234,831	209,324	200,690
Amortization of deferred policy acquisition costs and value of business acquired									0	0	$ 0
Operating Segment Assets
Investments and other assets	12,715,208				15,043,597				12,715,208	15,043,597
Deferred policy acquisition costs and value of business acquired	0				0				0	0
Other intangibles	31,934				35,256				31,934	35,256
Goodwill	0				0				0	0
Total assets	$ 12,747,142				$ 15,078,853				$ 12,747,142	$ 15,078,853