SIGNIFICANT ACCOUNTING POLICIES SIGNIFICANT ACCOUTNING POLICIES - Schedule of Accounting Change Adjustments made to the Consolidated Statements of Equity (Details) - USD ($) $ in Millions	3 Months Ended						6 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Jun. 30, 2017	Jun. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Equity	$ 15,959	$ 11,100	$ 14,227	$ 17,764	$ 17,744	$ 17,183	$ 11,100	$ 17,744	$ 15,959	$ 17,764	$ 14,379	$ 15,530	$ 16,387
Net income (loss)	66	1,714	(120)	137	576	1,067	1,593	1,642	1,677	1,779	524	1,070	3,100
Other comprehensive income (loss)	(52)	295	143	15	605	726	438	1,331	380	1,345	(201)	(860)	847
Current and deferred income taxes			(224)			380	224	376	639	93	(841)	42	737
Other Noncash Income (Expense)									(711)	(341)
(Decrease) increase in overdrafts payable									66	(75)
Net cash provided by (used in) financing activities									5,460	4,929
Amortization of deferred cost of reinsurance asset									111	115
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, As Revised		16,109		17,766	17,744	17,182	16,109	17,744		17,766
Noncontrolling Interest
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Equity	2,969			3,012					2,969	3,012	(3,096)	(3,059)
Other comprehensive income (loss)									19	1
Dividends									347	287
Net income (loss) attributable to noncontrolling interest									311	326
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders									(96)	(92)
Parent
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Equity	12,990	13,116	11,181	14,752	14,733	14,140	13,116	14,733	12,990	14,752	11,283	12,471	13,425
AOCI Attributable to Parent
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accumulated other comprehensive income, beginning of year after accounting change											1	185	258	$ (618)
Equity	362	452	137	1,529	1,516	908	452	1,516	362	1,529	1	208
Other comprehensive income (loss)			136			723	451	1,331	361	1,344	(184)	(845)	876
Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Adjusted Balance, Revised											6,058	6,963
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Adjusted Balance, Revised											5,938	6,963
Accumulated other comprehensive income, beginning of year after accounting change											5,941	6,963	7,208	4,876
Equity	7,265	7,301	5,700	7,908	7,897	7,913	7,301	7,897	7,265	7,908	5,941	8,896
Net income (loss)			(238)			950	1,362	1,434		1,445	28	667	2,713
Dividends									0	500	(1,050)	(912)	(381)
Additional Paid-in Capital
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Equity	$ 5,361			5,313					5,361	5,313	5,339	5,321
Deferred tax on dividend of AB Units									$ 0
As previously reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Equity		12,608	15,969	20,883	21,013	19,963	12,608	21,013		20,883	16,416	17,595	18,108
Net income (loss)		1,459	(313)	22	1,061	1,720	1,146	2,781		2,803	544	1,464	4,420
Other comprehensive income (loss)			179	(23)	620	789		1,409		1,386	(238)	(910)	925
Current and deferred income taxes			(327)			733	(16)	985		704	(771)	258	1,448
Other Noncash Income (Expense)			0			(50)	0	(119)			(31)	(111)	98
(Decrease) increase in overdrafts payable			50			0	0	0			(85)	0	0
Net cash provided by (used in) financing activities			2,306			1,468	0	4,016			5,751	3,034	3,843
Amortization of deferred cost of reinsurance asset											159	39	302
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, As Revised		17,617			21,013		17,617	21,013
As previously reported | Noncontrolling Interest
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Equity		0	3,035	3,001	3,026	3,069	0	3,026		3,001	3,085	3,086	2,989	2,903
Net income (loss) attributable to noncontrolling interest			118			117	118	203		299	464	403	387
As previously reported | Parent
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Equity		14,635	12,934	17,882	17,987	16,894	14,635	17,987		17,882	13,331	14,509	15,119
As previously reported | AOCI Attributable to Parent
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Equity		493			1,637		493	1,637			7	228	351	(603)
Other comprehensive income (loss)			172			786	486	1,409		1,385	(221)	(895)	954
As previously reported | Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Adjusted Balance, Revised											7,842	8,958
Equity		8,779	7,411	10,954	11,030	10,561	8,779	11,030		10,954		8,958	8,809	5,205
Net income (loss)			(431)			1,603	915	2,572		2,496	75	1,061	4,033
Dividends											(1,050)	(912)	(429)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, As Revised											7,983	8,958	8,809
As previously reported | Additional Paid-in Capital
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Equity											5,339	5,321	5,957	5,934
Deferred tax on dividend of AB Units											0	(35)	(26)
Impact of Revision
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Equity		(84)	(53)	(72)	(110)		(84)	(110)		(72)	(192)	(109)	(100)
Net income (loss)		(9)	1	11	(21)	16	(9)	(5)		6	(114)	11	(139)
Other comprehensive income (loss)			0	30	(15)	6		(9)		20	20	(20)	0
Current and deferred income taxes			0			8	(5)	1		(57)	(121)	2	(75)
Other Noncash Income (Expense)			0			(91)	0	48			0	80	(39)
(Decrease) increase in overdrafts payable			0			(91)	0	48			0	80	(39)
Net cash provided by (used in) financing activities			0			(91)	0	48			0	80	(39)
Amortization of deferred cost of reinsurance asset													(10)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, As Revised		(84)			(110)	(86)	(84)	(110)
Impact of Revision | Noncontrolling Interest
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Equity		11	11	11	(15)	(27)	11	(15)		11	11	(27)	(27)	21
Net income (loss) attributable to noncontrolling interest			0			0	0	1		27	27	0	0
Impact of Revision | Parent
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Equity		(95)	(64)	(83)	(95)	(60)	(95)	(95)		(83)	(203)	(82)	(73)
Impact of Revision | AOCI Attributable to Parent
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Equity		0	0		(29)		0	(29)			0	(20)	0	0
Other comprehensive income (loss)			0			6	0	(9)		20	20	(20)
Impact of Revision | Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Adjusted Balance, Revised			(65)									(62)
Equity		(95)	(64)	(83)	(66)	(46)	(95)	(66)		(83)	(203)	(62)	(73)	18
Net income (loss)			1			16	(9)	(4)		(21)	(141)	11
Other comprehensive income (loss)													0
Dividends											0	0	48
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, As Revised												(62)	(73)
Impact of Revision | Additional Paid-in Capital
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Equity											0	0	0	(26)
Deferred tax on dividend of AB Units											0	0	26
As Revised
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Equity		12,524	15,916	20,811	20,903	19,877	12,524	20,903		20,811	16,224	17,486	18,008
Net income (loss)		1,450	(312)	33	1,040	1,736	1,137	2,776		2,809	430	1,475	4,281
Other comprehensive income (loss)		294	179	7	605	795	473	1,400		1,406	(218)	(930)	925
Current and deferred income taxes			(327)			741	(21)	986		647	(892)	260	1,373
Other Noncash Income (Expense)							0	(71)			(31)	(31)	59
(Decrease) increase in overdrafts payable			50			(91)	0	48			(85)	80	(39)
Net cash provided by (used in) financing activities			2,306			1,377	0	4,064			5,751	3,114	3,804
Amortization of deferred cost of reinsurance asset											159	121	292
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, As Revised		17,533		20,811	20,903	19,876	17,533	20,903		20,811
As Revised | Noncontrolling Interest
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Equity		11	3,046	3,012	3,011	3,042	11	3,011		3,012	3,096	3,059	2,962	2,924
Net income (loss) attributable to noncontrolling interest			118			117	118	204		326	491	403	387
As Revised | Parent
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Equity		14,540	12,870	17,799	17,892	16,834	14,540	17,892		17,799	13,128	14,427	15,046
As Revised | AOCI Attributable to Parent
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accumulated other comprehensive income, beginning of year after accounting change											7	208	351	(603)
Equity		493	179	1,613	1,608	1,000	493	1,608		1,613	7	208	351	(603)
Other comprehensive income (loss)			172			792	486	1,400		1,405	(201)	(915)	954
As Revised | Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Adjusted Balance, Revised											7,897	8,896
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Adjusted Balance, Revised											7,777	8,896
Accumulated other comprehensive income, beginning of year after accounting change											7,780	8,896	8,736	5,223
Equity		8,684	7,347	10,871	10,964	10,515	8,684	10,964		10,871	7,780	8,896	8,736	5,223
Net income (loss)			(430)			1,619	906	2,568		2,475	(66)	1,072	3,894
Dividends											(1,050)	(912)	(381)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, As Revised												8,896	8,736
As Revised | Additional Paid-in Capital
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Equity											5,339	5,321	5,957	5,908
Deferred tax on dividend of AB Units											0	(35)	0
Impact of Revision
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Equity		(1,424)	(1,689)		(3,159)	(2,694)	(1,424)	(3,159)			(1,845)	(1,956)	(1,621)
Stockholders' Equity, Including Portion Attributable To Noncontrolling Interest, Adjustment				0						0
Net income (loss)		264	192	104	(464)	(669)	456	(1,134)		(1,030)	94	(405)	(1,181)
Other comprehensive income (loss)		1	(36)	8	0	(69)	(35)	(69)		(61)	17	70	(78)
Current and deferred income taxes			103			(361)	245	(610)		(554)	51	(218)	(636)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, As Revised		(1,424)		(3,045)	(3,159)		(1,424)	(3,159)		(3,045)
Impact of Revision | Parent
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Equity		(1,424)	(1,689)	(5,926)	(3,159)	(2,694)	(1,424)	(3,159)		(5,926)	(1,845)	(1,956)	(1,621)
Impact of Revision | AOCI Attributable to Parent
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accumulated other comprehensive income, beginning of year after accounting change											(6)	(23)	(93)	(15)
Equity		(41)	(42)	(84)	(92)	(92)	(41)	(92)		(84)
Other comprehensive income (loss)			(36)			(69)	(35)	(69)		(61)	17	70	(78)
Impact of Revision | Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Adjusted Balance, Revised											(1,839)	(1,933)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Adjusted Balance, Revised											(1,839)	(1,933)
Accumulated other comprehensive income, beginning of year after accounting change											(1,839)	(1,933)	(1,528)	$ (347)
Equity		$ (1,383)	(1,647)	$ (2,963)	$ (3,067)	(2,602)	(1,383)	(3,067)		(2,963)
Net income (loss)			$ 192			$ (669)	$ 456	$ (1,134)		$ (1,030)	94	(405)	(1,181)
Dividends											$ 0	$ 0	$ 0