Fair Value Measurements - Other Financial Instruments (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	$ 122	$ 128
Other investments	35	40
Assets held in separate accounts	73,369	67,323
Derivatives liabilities	182	99
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturities, including securities pledged	25,902	25,034
Equity securities	87	57
Cash and cash equivalents, short-term investments and short-term investments under securities loan agreement	1,400	1,207
Derivative assets	122	128
Short-term loan affiliate	103	0
Other investments	35	40
Assets held in separate accounts	73,369	67,323
Deposit liabilities	77	77
Derivatives liabilities	182	99
Short-term Debt	1	1
Long-term debt	4	4
Carrying Value | Embedded derivative on reinsurance
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Embedded derivative on reinsurance	(41)	(80)
Carrying Value | Funding agreements without fixed maturities and deferred annuities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities	25,920	26,068
Carrying Value | Funding agreements with fixed maturities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities	687	658
Carrying Value | Supplementary contracts, immediate annuities and other
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities	579	333
Carrying Value | FIA
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities	11	11
Carrying Value | Stabilizer and MCGs
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities	4	4
Carrying Value | Mortgage loans on real estate
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	4,811	4,918
Carrying Value | Policy loans
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	207	210
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturities, including securities pledged	25,902	25,034
Equity securities	87	57
Cash and cash equivalents, short-term investments and short-term investments under securities loan agreement	1,400	1,207
Derivative assets	122	128
Short-term loan affiliate	103	0
Other investments	35	40
Assets held in separate accounts	73,369	67,323
Deposit liabilities	126	122
Derivatives liabilities	182	99
Short-term Debt	1	1
Long-term debt	4	4
Fair Value | Embedded derivative on reinsurance
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Embedded derivative on reinsurance	(41)	(80)
Fair Value | Funding agreements without fixed maturities and deferred annuities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities	29,990	29,108
Fair Value | Funding agreements with fixed maturities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities	685	652
Fair Value | Supplementary contracts, immediate annuities and other
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities	679	354
Fair Value | FIA
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities	11	11
Fair Value | Stabilizer and MCGs
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities	4	4
Fair Value | Mortgage loans on real estate
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	4,930	4,983
Fair Value | Policy loans
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	$ 207	$ 210