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
	Mar. 31, 2018	Mar. 31, 2017
Gains (losses) included in net income for Level 3 assets and liabilities:
Total recurring Level 3 assets	$ 1	$ 5
Total recurring Level 3 liabilities	23	3
Fair value, assets and liabilities gain (loss) included in earnings	24	8
Gain (loss) on investments
Gains (losses) included in net income for Level 3 assets and liabilities:
Fair value, assets and liabilities gain (loss) included in earnings	24	8
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	1	1
(Loss) gain reclassified from AOCI into income (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		5
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	19	(5)
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	4	7
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	23	3
Equity securities
Gains (losses) included in net income for Level 3 assets and liabilities:
Total recurring Level 3 assets	1	5
Free-standing derivatives, net
Gains (losses) included in net income for Level 3 assets and liabilities:
Total recurring Level 3 assets	0	1
Other assets
Gains (losses) included in net income for Level 3 assets and liabilities:
Total recurring Level 3 assets	$ 0	$ (1)