FAIR VALUE DISCLOSURES - Textual (Details) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Quantitative Disclosure [Line Items]
Fixed maturities, available-for-sale			$ 36,515,000,000
Fair value freestanding contract	$ 1,938,000,000		$ 1,953,000,000
Freestanding contract invested assets (as a percent)	44.80%		48.50%
Fair value adjustments on GMIB asset	$ 118,000,000		$ 69,000,000
Transfers out of Level 3	16,000,000	$ 0
Transfers into level 3	$ 67,000,000	$ 15,000,000
Transfers out of Levels 2 and 3 to total equity (as a percent)	0.40%	0.10%
Investments which the underlying quantitative inputs are not developed by the Company and are not readily available	$ 497,000,000		$ 395,000,000
Percentage of total assets classified as Level 3	29.80%		25.30%
Percentage of assets measured at fair value on a recurring basis	0.30%		0.20%
2016 Acquisition | Contingent Payment Arrangement
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Quantitative Disclosure [Line Items]
Acquisition-related contingent consideration liability			$ 11,000,000
Revenue growth rate			31.00%
2016 Acquisition | Contingent Payment Arrangement | Minimum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Quantitative Disclosure [Line Items]
Discount rate			1.40%
2016 Acquisition | Contingent Payment Arrangement | Maximum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Quantitative Disclosure [Line Items]
Discount rate			2.30%
Corporate | Private Available For Sale Corporate Securities | Matrix pricing model
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Quantitative Disclosure [Line Items]
Fair value of privately placed, available-for-sale corporate debt securities classified as Level 3	$ 840,000,000		$ 842,000,000
Percentage of Level 3 securities in the corporate fixed maturities asset class	68.30%		73.90%
Asset-backed | Matrix pricing model
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Quantitative Disclosure [Line Items]
Percentage of Level 3 securities in the corporate fixed maturities asset class
Separate Accounts Assets | Third party appraisal
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Quantitative Disclosure [Line Items]
Discount rate	6.50%		6.60%
Separate Accounts Assets | Asset-backed
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Quantitative Disclosure [Line Items]
Fair value of privately placed, available-for-sale corporate debt securities classified as Level 3	$ 9,000,000		$ 8,000,000
Separate Accounts Assets | Collateralized Mortgage Backed Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Quantitative Disclosure [Line Items]
Fair value of privately placed, available-for-sale corporate debt securities classified as Level 3	15,000,000		14,000,000
Separate Accounts Assets | Private Real Estate Fund | Third party appraisal
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Quantitative Disclosure [Line Items]
Fair value of privately placed, available-for-sale corporate debt securities classified as Level 3	332,000,000		326,000,000
Separate Accounts Assets | Mortgages | Third party appraisal
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Quantitative Disclosure [Line Items]
Fair value of privately placed, available-for-sale corporate debt securities classified as Level 3	$ 1,000,000		$ 1,000,000
Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Quantitative Disclosure [Line Items]
Assets measured at fair value on recurring basis (as a percent)	69.90%		69.20%
Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Quantitative Disclosure [Line Items]
Assets measured at fair value on recurring basis (as a percent)	29.10%		29.90%
Mortgages and asset-backed securities owned	$ 313,000,000		$ 257,000,000
Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Quantitative Disclosure [Line Items]
Assets measured at fair value on recurring basis (as a percent)	1.00%		0.90%
Mortgages and asset-backed securities owned	$ 7,000,000		$ 8,000,000
Fair value disclosures broker priced	95,000,000		97,000,000
Level 3 | Corporate | Matrix pricing model
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Quantitative Disclosure [Line Items]
Fair value of privately placed, available-for-sale corporate debt securities classified as Level 3	52,000,000		53,000,000
Level 3 | Separate Accounts Assets | Third party appraisal
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Quantitative Disclosure [Line Items]
Fair value of privately placed, available-for-sale corporate debt securities classified as Level 3	332,000,000		326,000,000
Public Fixed Maturities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Quantitative Disclosure [Line Items]
Fixed maturities, available-for-sale	$ 26,174,000,000		$ 28,826,000,000
Available-for-sale fixed maturity assets measured at fair value on recurring basis (as a percent)	15.00%		16.20%
Private Fixed Maturities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Quantitative Disclosure [Line Items]
Fixed maturities, available-for-sale	$ 7,456,000,000		$ 7,532,000,000
Available-for-sale fixed maturity assets measured at fair value on recurring basis (as a percent)	4.30%		4.20%