Fair Value of Assets and Liabilities - Change In Unrealized Gains and Losses included in Net Income for Level 3 (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Gains (losses) included in net income for Level 3 assets and liabilities:
Total recurring Level 3 assets	$ 3	$ (1)	$ 10	$ 8
Total recurring Level 3 liabilities	(6)	(8)	19	(5)
Contractholder funds: Derivatives embedded in life and annuity contracts
Gains (losses) included in net income for Level 3 assets and liabilities:
Total recurring Level 3 liabilities	(6)	(8)	19	(5)
Corporate
Gains (losses) included in net income for Level 3 assets and liabilities:
Total recurring Level 3 assets	0	1	0	1
Equity securities
Gains (losses) included in net income for Level 3 assets and liabilities:
Total recurring Level 3 assets	3	1	10	8
Free-standing derivatives, net
Gains (losses) included in net income for Level 3 assets and liabilities:
Total recurring Level 3 assets	0	(3)	0	0
Other assets
Gains (losses) included in net income for Level 3 assets and liabilities:
Total recurring Level 3 assets	$ 0	$ 0	$ 0	$ (1)