Investments Investments - Narrative (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Fair value of assets and liabilities measured on recurring and non-recurring basis
Gross gains on sales of fixed income securities, debt	$ 13,000,000	$ 13,000,000	$ 26,000,000	$ 20,000,000
Gross losses on sales of fixed income securities, debt	(6,000,000)	24,000,000	(25,000,000)	36,000,000
Net unrealized gains related to changes in valuation of fixed income securities subsequent to impairment measurement date	103,000,000		103,000,000		$ 101,000,000
Limited partnership interests	3,275,000,000		3,275,000,000		3,292,000,000
Short-term investments	1,217,000,000		1,217,000,000		810,000,000
Policy loans	548,000,000		548,000,000		561,000,000
Other	1,352,000,000		1,352,000,000		1,300,000,000
Equity method limited partnerships
Fair value of assets and liabilities measured on recurring and non-recurring basis
Limited partnership interests	2,500,000,000		2,500,000,000		2,510,000,000
Carrying value | Cost method limited partnership interests
Fair value of assets and liabilities measured on recurring and non-recurring basis
Limited partnership interests	773,000,000		773,000,000		$ 787,000,000
Non-impaired mortgage loans
Fair value of assets and liabilities measured on recurring and non-recurring basis
Allowance for credit losses, period increase (decrease)	$ 0	$ 0	0	0
Mortgage loans
Fair value of assets and liabilities measured on recurring and non-recurring basis
Average balance impaired mortgage loans			$ 4,000,000	$ 4,000,000