Fair Value of Assets and Liabilities - Change in unrealized gains and losses (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Gains (losses) included in net income for Level 3 assets and liabilities:
Gains (losses) for Level 3 assets still held at the balance sheet date, included in earnings	$ 16	$ 9	$ (7)
Gains (losses) for Level 3 liabilities still held at the balance sheet date, included in earnings	57	1	6
Gains (losses) for Level 3 assets and liabilities still held at the balance sheet date	73	10	(1)
Net investment income
Gains (losses) included in net income for Level 3 assets and liabilities:
Gains (losses) for Level 3 assets and liabilities still held at the balance sheet date		10	11
Interest credited to contractholder funds
Gains (losses) included in net income for Level 3 assets and liabilities:
Gains (losses) for Level 3 assets and liabilities still held at the balance sheet date	62	(9)	(3)
Contract benefits
Gains (losses) included in net income for Level 3 assets and liabilities:
Gains (losses) for Level 3 assets and liabilities still held at the balance sheet date	(5)	9	9
Realized capital gains and losses
Gains (losses) included in net income for Level 3 assets and liabilities:
Gains (losses) for Level 3 assets and liabilities still held at the balance sheet date	16		(18)
Municipal
Gains (losses) included in net income for Level 3 assets and liabilities:
Gains (losses) for Level 3 assets still held at the balance sheet date, included in earnings	0	0	2
Corporate
Gains (losses) included in net income for Level 3 assets and liabilities:
Gains (losses) for Level 3 assets still held at the balance sheet date, included in earnings	0	1	1
Fixed income securities
Gains (losses) included in net income for Level 3 assets and liabilities:
Gains (losses) for Level 3 assets still held at the balance sheet date, included in earnings	0	1	3
Equity securities
Gains (losses) included in net income for Level 3 assets and liabilities:
Gains (losses) for Level 3 assets still held at the balance sheet date, included in earnings	16	9	(15)
Free-standing derivatives, net
Gains (losses) included in net income for Level 3 assets and liabilities:
Gains (losses) for Level 3 assets still held at the balance sheet date, included in earnings	0	0	5
Other assets
Gains (losses) included in net income for Level 3 assets and liabilities:
Gains (losses) for Level 3 assets still held at the balance sheet date, included in earnings	0	(1)	0
Contractholder funds: 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	$ 57	$ 1	$ 6