OPERATING SEGMENTS (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Summarized financial information for the company's segments
Revenues	$ 1,243,908	$ 1,087,067	$ 2,409,740	$ 2,192,364
Pre-tax Adjusted Operating Income (Loss)	116,596	146,134	209,417	281,523
Realized (losses) gains on investments and derivatives	(17,824)	(20,366)	(18,847)	(43,406)
Income before income tax	98,772	125,768	190,570	238,117
Income tax expense	(17,277)	(41,500)	(34,963)	(78,435)
Net income	81,495	84,268	155,607	159,682
Adjusted operating income tax (expense) benefit	(20,877)	(48,628)	(38,920)	(93,627)
After-tax adjusted operating income	95,719	97,506	170,497	187,896
Income tax benefit (expense) on adjustments	3,600	7,128	3,957	15,192
Realized investment (losses) gains:
Derivative financial instruments	12,265	(108,188)	90,324	(178,066)
All other investments	(49,602)	53,717	(137,201)	76,558
Net impairment losses recognized in earnings	(5)	(2,785)	(3,650)	(10,616)
Less: related amortization	1,763	(15,703)	10,919	(26,447)
Less: VA GLWB economic cost	(21,281)	(21,187)	(42,599)	(42,271)
Operating Segment Assets
Investments and other assets	86,721,685		86,721,685		$ 75,973,148
DAC and VOBA	2,870,620		2,870,620		2,199,577
Other intangibles	639,538		639,538		663,572
Goodwill	793,470		793,470		793,470
Total assets	91,025,313		91,025,313		79,629,767
Life Marketing
Summarized financial information for the company's segments
Revenues	414,954	407,046	849,870	828,438
Pre-tax Adjusted Operating Income (Loss)	(7,737)	23,243	(25,586)	42,188
Operating Segment Assets
Investments and other assets	14,652,367		14,652,367		14,914,418
DAC and VOBA	1,421,313		1,421,313		1,320,776
Other intangibles	272,592		272,592		282,361
Goodwill	200,274		200,274		200,274
Total assets	16,546,546		16,546,546		16,717,829
Acquisitions
Summarized financial information for the company's segments
Revenues	509,639	387,464	888,733	788,831
Pre-tax Adjusted Operating Income (Loss)	59,038	68,278	114,558	121,945
Operating Segment Assets
Investments and other assets	32,435,800		32,435,800		19,588,133
DAC and VOBA	437,538		437,538		74,862
Other intangibles	33,267		33,267		34,548
Goodwill	14,524		14,524		14,524
Total assets	32,921,129		32,921,129		19,712,067
Annuities
Summarized financial information for the company's segments
Revenues	133,177	112,322	283,890	220,964
Pre-tax Adjusted Operating Income (Loss)	55,934	46,578	96,465	99,585
Operating Segment Assets
Investments and other assets	20,770,915		20,770,915		20,938,409
DAC and VOBA	840,715		840,715		772,634
Other intangibles	163,451		163,451		170,117
Goodwill	336,677		336,677		336,677
Total assets	22,111,758		22,111,758		22,217,837
Stable Value Products
Summarized financial information for the company's segments
Revenues	45,748	42,087	99,616	82,930
Pre-tax Adjusted Operating Income (Loss)	19,992	22,367	49,072	46,266
Operating Segment Assets
Investments and other assets	4,897,132		4,897,132		4,569,639
DAC and VOBA	7,284		7,284		6,864
Other intangibles	7,722		7,722		8,056
Goodwill	113,813		113,813		113,813
Total assets	5,025,951		5,025,951		4,698,372
Asset Protection
Summarized financial information for the company's segments
Revenues	77,814	82,462	154,189	162,545
Pre-tax Adjusted Operating Income (Loss)	7,166	6,536	13,384	12,135
Operating Segment Assets
Investments and other assets	1,019,950		1,019,950		918,952
DAC and VOBA	163,770		163,770		24,441
Other intangibles	127,912		127,912		133,234
Goodwill	128,182		128,182		128,182
Total assets	1,439,814		1,439,814		1,204,809
Corporate and Other
Summarized financial information for the company's segments
Revenues	62,576	55,686	133,442	108,656
Pre-tax Adjusted Operating Income (Loss)	(17,797)	$ (20,868)	(38,476)	$ (40,596)
Operating Segment Assets
Investments and other assets	12,945,521		12,945,521		15,043,597
DAC and VOBA	0		0		0
Other intangibles	34,594		34,594		35,256
Goodwill	0		0		0
Total assets	$ 12,980,115		$ 12,980,115		$ 15,078,853