INVESTMENTS - MORTGAGE LOANS (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
Mar. 31, 2018	Dec. 31, 2017
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	$ 712
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	712
Commercial Mortgage Loans
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	8,738	$ 8,369
Financing Receivable, Recorded Investment, Aging [Abstract]
Financing receivables, recorded investment, past due	27	27
Financing receivables, recorded investment, current	8,711	8,342
Total Financing Receivables	8,738	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
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	5,365	4,999
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	5,365	4,999
Commercial Mortgage Loans \| 1.8x to 2.0x
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	775	792
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	775	792
Commercial Mortgage Loans \| 1.5x to 1.8x
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	1,614	1,609
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	1,614	1,609
Commercial Mortgage Loans \| 1.2x to 1.5x
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	779	774
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	779	774
Commercial Mortgage Loans \| 1.0x to 1.2x
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	205	195
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	205	195
Commercial Mortgage Loans \| Less than 1.0x
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%
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	1,135	1,136
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	1,135	1,136
Commercial Mortgage Loans \| 0% - 50% \| Greater than 2.0x
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	719	742
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	719	742
Commercial Mortgage Loans \| 0% - 50% \| 1.8x to 2.0x
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	22	0
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	22	0
Commercial Mortgage Loans \| 0% - 50% \| 1.5x to 1.8x
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	321	320
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	321	320
Commercial Mortgage Loans \| 0% - 50% \| 1.2x to 1.5x
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	73	74
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	73	74
Commercial Mortgage Loans \| 0% - 50% \| 1.0x to 1.2x
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
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%
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	6,819	6,409
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	6,819	6,409
Commercial Mortgage Loans \| 50% - 70% \| Greater than 2.0x
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	4,477	4,088
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	4,477	4,088
Commercial Mortgage Loans \| 50% - 70% \| 1.8x to 2.0x
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	643	682
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	643	682
Commercial Mortgage Loans \| 50% - 70% \| 1.5x to 1.8x
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	1,122	1,066
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	1,122	1,066
Commercial Mortgage Loans \| 50% - 70% \| 1.2x to 1.5x
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	399	428
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	399	428
Commercial Mortgage Loans \| 50% - 70% \| 1.0x to 1.2x
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	178	145
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	178	145
Commercial Mortgage Loans \| 50% - 70% \| Less than 1.0x
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%
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	757	797
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	757	797
Commercial Mortgage Loans \| 70% - 90% \| Greater than 2.0x
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	169	169
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	169	169
Commercial Mortgage Loans \| 70% - 90% \| 1.8x to 2.0x
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
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	144	196
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	144	196
Commercial Mortgage Loans \| 70% - 90% \| 1.2x to 1.5x
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	307	272
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	307	272
Commercial Mortgage Loans \| 70% - 90% \| 1.0x to 1.2x
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
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
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
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
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
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
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
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
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
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	2,585	2,574
Financing Receivable, Recorded Investment, Aging [Abstract]
Financing receivables, recorded investment, past due	54	74
Financing receivables, recorded investment, current	2,531	2,500
Total Financing Receivables	2,585	2,574
Financing receivable, recorded investment, 90 days or more past due and accruing	39	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	10	49
Agricultural Mortgage Loans \| 60-89 Days
Financing Receivable, Recorded Investment, Aging [Abstract]
Financing receivables, recorded investment, past due	5	3
Agricultural Mortgage Loans \| 90 Days or More
Financing Receivable, Recorded Investment, Aging [Abstract]
Financing receivables, recorded investment, past due	39	22
Agricultural Mortgage Loans \| Greater than 2.0x
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	386	383
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	386	383
Agricultural Mortgage Loans \| 1.8x to 2.0x
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	199	195
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	199	195
Agricultural Mortgage Loans \| 1.5x to 1.8x
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	495	502
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	495	502
Agricultural Mortgage Loans \| 1.2x to 1.5x
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	879	878
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	879	878
Agricultural Mortgage Loans \| 1.0x to 1.2x
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	549	537
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	549	537
Agricultural Mortgage Loans \| Less than 1.0x
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	77	79
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	77	79
Agricultural Mortgage Loans \| 0% - 50%
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	1,550	1,557
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	1,550	1,557
Agricultural Mortgage Loans \| 0% - 50% \| Greater than 2.0x
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	275	272
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	275	272
Agricultural Mortgage Loans \| 0% - 50% \| 1.8x to 2.0x
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	153	149
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	153	149
Agricultural Mortgage Loans \| 0% - 50% \| 1.5x to 1.8x
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	276	275
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	276	275
Agricultural Mortgage Loans \| 0% - 50% \| 1.2x to 1.5x
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	496	515
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	496	515
Agricultural Mortgage Loans \| 0% - 50% \| 1.0x to 1.2x
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	321	316
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	321	316
Agricultural Mortgage Loans \| 0% - 50% \| Less than 1.0x
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	29	30
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	29	30
Agricultural Mortgage Loans \| 50% - 70%
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	1,012	1,013
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	1,012	1,013
Agricultural Mortgage Loans \| 50% - 70% \| Greater than 2.0x
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	111	111
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	111	111
Agricultural Mortgage Loans \| 50% - 70% \| 1.8x to 2.0x
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	46	46
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	46	46
Agricultural Mortgage Loans \| 50% - 70% \| 1.5x to 1.8x
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	219	227
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	219	227
Agricultural Mortgage Loans \| 50% - 70% \| 1.2x to 1.5x
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	360	359
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	360	359
Agricultural Mortgage Loans \| 50% - 70% \| 1.0x to 1.2x
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	228	221
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	228	221
Agricultural Mortgage Loans \| 50% - 70% \| Less than 1.0x
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	48	49
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	48	49
Agricultural Mortgage Loans \| 70% - 90%
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	23	4
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	23	4
Agricultural Mortgage Loans \| 70% - 90% \| Greater than 2.0x
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
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
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
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	23	4
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	23	4
Agricultural Mortgage Loans \| 70% - 90% \| 1.0x to 1.2x
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
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
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
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
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
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
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
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
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
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	11,323	10,943
Financing Receivable, Recorded Investment, Aging [Abstract]
Financing receivables, recorded investment, past due	81	101
Financing receivables, recorded investment, current	11,242	10,842
Total Financing Receivables	11,323	10,943
Financing receivable, recorded investment, 90 days or more past due and accruing	39	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	10	76
Total Mortgages Loan \| 60-89 Days
Financing Receivable, Recorded Investment, Aging [Abstract]
Financing receivables, recorded investment, past due	5	3
Total Mortgages Loan \| 90 Days or More
Financing Receivable, Recorded Investment, Aging [Abstract]
Financing receivables, recorded investment, past due	66	22
Total Mortgages Loan \| Greater than 2.0x
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	5,751	5,382
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	5,751	5,382
Total Mortgages Loan \| 1.8x to 2.0x
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	974	987
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	974	987
Total Mortgages Loan \| 1.5x to 1.8x
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	2,109	2,111
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	2,109	2,111
Total Mortgages Loan \| 1.2x to 1.5x
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	1,658	1,652
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	1,658	1,652
Total Mortgages Loan \| 1.0x to 1.2x
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	754	732
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	754	732
Total Mortgages Loan \| Less than 1.0x
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	77	79
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	77	79
Total Mortgages Loan \| 0% - 50%
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	2,685	2,693
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	2,685	2,693
Total Mortgages Loan \| 0% - 50% \| Greater than 2.0x
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	994	1,014
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	994	1,014
Total Mortgages Loan \| 0% - 50% \| 1.8x to 2.0x
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	175	149
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	175	149
Total Mortgages Loan \| 0% - 50% \| 1.5x to 1.8x
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	597	595
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	597	595
Total Mortgages Loan \| 0% - 50% \| 1.2x to 1.5x
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	569	589
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	569	589
Total Mortgages Loan \| 0% - 50% \| 1.0x to 1.2x
Mortgage Loans on Real Estate [Line Items]
Total Mortgage Loans	321	316
Financing Receivable, Recorded Investment, Aging [Abstract]
Total Financing Receivables	321	316
Total Mortgages Loan \| 0% - 50% \| Less than 1.0x
Mortgage Loans on Real Estate [Line Items]

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

3 Months Ended

12 Months Ended

Mar. 31, 2018

Dec. 31, 2017

Mortgage Loans on Real Estate [Line Items]

Total Mortgage Loans

$ 712

Financing Receivable, Recorded Investment, Aging [Abstract]

Total Financing Receivables

712

Commercial Mortgage Loans