INVESTMENTS - MORTGAGE LOANS (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
Sep. 30, 2018	Dec. 31, 2017
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	$ 379
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	379
Commercial Mortgage Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	9,388	$ 8,369
Financing Receivable, Recorded Investment, Aging [Abstract]
Financing receivables, recorded investment, past due	27	27
Financing receivables, recorded investment, current	9,361	8,342
Total Financing Receivables	9,388	8,369
Financing receivable, recorded investment, 90 days or more past due and accruing	0	0
Commercial Mortgage Loans \| With no related allowance recorded
Impaired Mortgage Loans [Abstract]
Recorded Investment	0	0
Unpaid Principal Balance	0	0
Related Allowance	0	0
Average Recorded Investment	0	0
Interest Income Recognized	0	0
Commercial Mortgage Loans \| With related allowance recorded
Impaired Mortgage Loans [Abstract]
Recorded Investment	27	27
Unpaid Principal Balance	27	27
Related Allowance	(7)	(8)
Average Recorded Investment	27	27
Interest Income Recognized	0	2
Commercial Mortgage Loans \| 30-59 Days
Financing Receivable, Recorded Investment, Aging [Abstract]
Financing receivables, recorded investment, past due	0	27
Commercial Mortgage Loans \| 60-89 Days
Financing Receivable, Recorded Investment, Aging [Abstract]
Financing receivables, recorded investment, past due	0	0
Commercial Mortgage Loans \| 90 Days or More
Financing Receivable, Recorded Investment, Aging [Abstract]
Financing receivables, recorded investment, past due	27	0
Commercial Mortgage Loans \| Greater than 2.0x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	5,766	4,999
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	5,766	4,999
Commercial Mortgage Loans \| 1.8x to 2.0x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	780	792
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	780	792
Commercial Mortgage Loans \| 1.5x to 1.8x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	1,739	1,609
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	1,739	1,609
Commercial Mortgage Loans \| 1.2x to 1.5x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	925	774
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	925	774
Commercial Mortgage Loans \| 1.0x to 1.2x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	178	195
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	178	195
Commercial Mortgage Loans \| Less than 1.0x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	0	0
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	0	0
Commercial Mortgage Loans \| 0% - 50%
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	1,202	1,136
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	1,202	1,136
Commercial Mortgage Loans \| 0% - 50% \| Greater than 2.0x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	806	742
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	806	742
Commercial Mortgage Loans \| 0% - 50% \| 1.8x to 2.0x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	21	0
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	21	0
Commercial Mortgage Loans \| 0% - 50% \| 1.5x to 1.8x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	351	320
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	351	320
Commercial Mortgage Loans \| 0% - 50% \| 1.2x to 1.5x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	24	74
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	24	74
Commercial Mortgage Loans \| 0% - 50% \| 1.0x to 1.2x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	0	0
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	0	0
Commercial Mortgage Loans \| 0% - 50% \| Less than 1.0x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	0	0
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	0	0
Commercial Mortgage Loans \| 50% - 70%
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	7,334	6,409
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	7,334	6,409
Commercial Mortgage Loans \| 50% - 70% \| Greater than 2.0x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	4,739	4,088
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	4,739	4,088
Commercial Mortgage Loans \| 50% - 70% \| 1.8x to 2.0x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	649	682
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	649	682
Commercial Mortgage Loans \| 50% - 70% \| 1.5x to 1.8x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	1,192	1,066
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	1,192	1,066
Commercial Mortgage Loans \| 50% - 70% \| 1.2x to 1.5x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	603	428
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	603	428
Commercial Mortgage Loans \| 50% - 70% \| 1.0x to 1.2x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	151	145
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	151	145
Commercial Mortgage Loans \| 50% - 70% \| Less than 1.0x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	0	0
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	0	0
Commercial Mortgage Loans \| 70% - 90%
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	825	797
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	825	797
Commercial Mortgage Loans \| 70% - 90% \| Greater than 2.0x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	221	169
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	221	169
Commercial Mortgage Loans \| 70% - 90% \| 1.8x to 2.0x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	110	110
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	110	110
Commercial Mortgage Loans \| 70% - 90% \| 1.5x to 1.8x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	169	196
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	169	196
Commercial Mortgage Loans \| 70% - 90% \| 1.2x to 1.5x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	298	272
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	298	272
Commercial Mortgage Loans \| 70% - 90% \| 1.0x to 1.2x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	27	50
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	27	50
Commercial Mortgage Loans \| 70% - 90% \| Less than 1.0x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	0	0
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	0	0
Commercial Mortgage Loans \| 90% plus
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	27	27
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	27	27
Commercial Mortgage Loans \| 90% plus \| Greater than 2.0x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	0	0
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	0	0
Commercial Mortgage Loans \| 90% plus \| 1.8x to 2.0x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	0	0
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	0	0
Commercial Mortgage Loans \| 90% plus \| 1.5x to 1.8x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	27	27
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	27	27
Commercial Mortgage Loans \| 90% plus \| 1.2x to 1.5x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	0	0
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	0	0
Commercial Mortgage Loans \| 90% plus \| 1.0x to 1.2x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	0	0
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	0	0
Commercial Mortgage Loans \| 90% plus \| Less than 1.0x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	0	0
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	0	0
Agricultural Mortgage Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	2,672	2,574
Financing Receivable, Recorded Investment, Aging [Abstract]
Financing receivables, recorded investment, past due	74	74
Financing receivables, recorded investment, current	2,598	2,500
Total Financing Receivables	2,672	2,574
Financing receivable, recorded investment, 90 days or more past due and accruing	57	22
Agricultural Mortgage Loans \| With no related allowance recorded
Impaired Mortgage Loans [Abstract]
Recorded Investment	0	0
Unpaid Principal Balance	0	0
Related Allowance	0	0
Average Recorded Investment	0	0
Interest Income Recognized	0	0
Agricultural Mortgage Loans \| With related allowance recorded
Impaired Mortgage Loans [Abstract]
Recorded Investment	0	0
Unpaid Principal Balance	0	0
Related Allowance	0	0
Average Recorded Investment	0	0
Interest Income Recognized	0	0
Agricultural Mortgage Loans \| 30-59 Days
Financing Receivable, Recorded Investment, Aging [Abstract]
Financing receivables, recorded investment, past due	5	49
Agricultural Mortgage Loans \| 60-89 Days
Financing Receivable, Recorded Investment, Aging [Abstract]
Financing receivables, recorded investment, past due	12	3
Agricultural Mortgage Loans \| 90 Days or More
Financing Receivable, Recorded Investment, Aging [Abstract]
Financing receivables, recorded investment, past due	57	22
Agricultural Mortgage Loans \| Greater than 2.0x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	398	383
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	398	383
Agricultural Mortgage Loans \| 1.8x to 2.0x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	195	195
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	195	195
Agricultural Mortgage Loans \| 1.5x to 1.8x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	488	502
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	488	502
Agricultural Mortgage Loans \| 1.2x to 1.5x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	952	878
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	952	878
Agricultural Mortgage Loans \| 1.0x to 1.2x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	557	537
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	557	537
Agricultural Mortgage Loans \| Less than 1.0x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	82	79
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	82	79
Agricultural Mortgage Loans \| 0% - 50%
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	1,580	1,557
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	1,580	1,557
Agricultural Mortgage Loans \| 0% - 50% \| Greater than 2.0x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	271	272
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	271	272
Agricultural Mortgage Loans \| 0% - 50% \| 1.8x to 2.0x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	142	149
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	142	149
Agricultural Mortgage Loans \| 0% - 50% \| 1.5x to 1.8x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	257	275
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	257	275
Agricultural Mortgage Loans \| 0% - 50% \| 1.2x to 1.5x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	555	515
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	555	515
Agricultural Mortgage Loans \| 0% - 50% \| 1.0x to 1.2x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	322	316
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	322	316
Agricultural Mortgage Loans \| 0% - 50% \| Less than 1.0x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	33	30
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	33	30
Agricultural Mortgage Loans \| 50% - 70%
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	1,073	1,013
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	1,073	1,013
Agricultural Mortgage Loans \| 50% - 70% \| Greater than 2.0x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	127	111
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	127	111
Agricultural Mortgage Loans \| 50% - 70% \| 1.8x to 2.0x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	53	46
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	53	46
Agricultural Mortgage Loans \| 50% - 70% \| 1.5x to 1.8x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	231	227
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	231	227
Agricultural Mortgage Loans \| 50% - 70% \| 1.2x to 1.5x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	378	359
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	378	359
Agricultural Mortgage Loans \| 50% - 70% \| 1.0x to 1.2x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	235	221
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	235	221
Agricultural Mortgage Loans \| 50% - 70% \| Less than 1.0x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	49	49
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	49	49
Agricultural Mortgage Loans \| 70% - 90%
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	19	4
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	19	4
Agricultural Mortgage Loans \| 70% - 90% \| Greater than 2.0x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	0	0
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	0	0
Agricultural Mortgage Loans \| 70% - 90% \| 1.8x to 2.0x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	0	0
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	0	0
Agricultural Mortgage Loans \| 70% - 90% \| 1.5x to 1.8x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	0	0
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	0	0
Agricultural Mortgage Loans \| 70% - 90% \| 1.2x to 1.5x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	19	4
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	19	4
Agricultural Mortgage Loans \| 70% - 90% \| 1.0x to 1.2x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	0	0
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	0	0
Agricultural Mortgage Loans \| 70% - 90% \| Less than 1.0x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	0	0
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	0	0
Agricultural Mortgage Loans \| 90% plus
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	0	0
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	0	0
Agricultural Mortgage Loans \| 90% plus \| Greater than 2.0x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	0	0
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	0	0
Agricultural Mortgage Loans \| 90% plus \| 1.8x to 2.0x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	0	0
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	0	0
Agricultural Mortgage Loans \| 90% plus \| 1.5x to 1.8x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	0	0
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	0	0
Agricultural Mortgage Loans \| 90% plus \| 1.2x to 1.5x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	0	0
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	0	0
Agricultural Mortgage Loans \| 90% plus \| 1.0x to 1.2x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	0	0
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	0	0
Agricultural Mortgage Loans \| 90% plus \| Less than 1.0x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	0	0
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	0	0
Total Mortgages Loan
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	12,060	10,943
Financing Receivable, Recorded Investment, Aging [Abstract]
Financing receivables, recorded investment, past due	101	101
Financing receivables, recorded investment, current	11,959	10,842
Total Financing Receivables	12,060	10,943
Financing receivable, recorded investment, 90 days or more past due and accruing	57	22
Total Mortgages Loan \| With no related allowance recorded
Impaired Mortgage Loans [Abstract]
Recorded Investment	0	0
Unpaid Principal Balance	0	0
Related Allowance	0	0
Average Recorded Investment	0	0
Interest Income Recognized	0	0
Total Mortgages Loan \| With related allowance recorded
Impaired Mortgage Loans [Abstract]
Recorded Investment	27	27
Unpaid Principal Balance	27	27
Related Allowance	(7)	(8)
Average Recorded Investment	27	27
Interest Income Recognized	0	2
Total Mortgages Loan \| 30-59 Days
Financing Receivable, Recorded Investment, Aging [Abstract]
Financing receivables, recorded investment, past due	5	76
Total Mortgages Loan \| 60-89 Days
Financing Receivable, Recorded Investment, Aging [Abstract]
Financing receivables, recorded investment, past due	12	3
Total Mortgages Loan \| 90 Days or More
Financing Receivable, Recorded Investment, Aging [Abstract]
Financing receivables, recorded investment, past due	84	22
Total Mortgages Loan \| Greater than 2.0x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	6,164	5,382
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	6,164	5,382
Total Mortgages Loan \| 1.8x to 2.0x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	975	987
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	975	987
Total Mortgages Loan \| 1.5x to 1.8x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	2,227	2,111
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	2,227	2,111
Total Mortgages Loan \| 1.2x to 1.5x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	1,877	1,652
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	1,877	1,652
Total Mortgages Loan \| 1.0x to 1.2x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	735	732
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	735	732
Total Mortgages Loan \| Less than 1.0x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	82	79
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	82	79
Total Mortgages Loan \| 0% - 50%
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	2,782	2,693
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	2,782	2,693
Total Mortgages Loan \| 0% - 50% \| Greater than 2.0x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	1,077	1,014
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	1,077	1,014
Total Mortgages Loan \| 0% - 50% \| 1.8x to 2.0x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	163	149
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	163	149
Total Mortgages Loan \| 0% - 50% \| 1.5x to 1.8x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	608	595
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	608	595
Total Mortgages Loan \| 0% - 50% \| 1.2x to 1.5x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	579	589
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	579	589
Total Mortgages Loan \| 0% - 50% \| 1.0x to 1.2x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	322	316
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	322	316
Total Mortgages Loan \| 0% - 50% \| Less than 1.0x
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]

INVESTMENTS - MORTGAGE LOANS (Details) - USD ($)
$ in Millions

9 Months Ended

12 Months Ended

Sep. 30, 2018

Dec. 31, 2017

SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]

Total Mortgage Loans

$ 379

Financing Receivable, Recorded Investment, Aging [Abstract]

Total Financing Receivables

379

Commercial Mortgage Loans