Fair Value of Assets and Liabilities - Change in unrealized gains and losses included in net income for level 3 assets and liabilities (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:
Recurring Level 3 assets	$ 8	$ 0	$ 23	$ 13
Gains (losses) for Level 3 liabilities still held at the balance sheet date, included in earnings	(7)	(9)	17	(6)
Derivatives embedded in life and annuity contracts
Gains (losses) included in net income for Level 3 assets and liabilities:
Gains (losses) for Level 3 liabilities still held at the balance sheet date, included in earnings	(7)	(9)	17	(6)
Municipal
Gains (losses) included in net income for Level 3 assets and liabilities:
Recurring Level 3 assets	0	0	0	(3)
Corporate
Gains (losses) included in net income for Level 3 assets and liabilities:
Recurring Level 3 assets	0	1	0	1
Fixed income securities
Gains (losses) included in net income for Level 3 assets and liabilities:
Recurring Level 3 assets	0	1	0	(2)
Equity securities
Gains (losses) included in net income for Level 3 assets and liabilities:
Recurring Level 3 assets	8	2	23	16
Free-standing derivatives, net
Gains (losses) included in net income for Level 3 assets and liabilities:
Recurring Level 3 assets	0	(3)	0	0
Other assets
Gains (losses) included in net income for Level 3 assets and liabilities:
Recurring Level 3 assets	$ 0	$ 0	$ 0	$ (1)