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
	Mar. 31, 2019	Mar. 31, 2018
Gains (losses) included in net income for Level 3 assets and liabilities:
Recurring Level 3 assets	$ 4	$ 2
Gains (losses) for Level 3 liabilities still held at the balance sheet date, included in earnings	(28)	23
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	(28)	23
Equity securities
Gains (losses) included in net income for Level 3 assets and liabilities:
Recurring Level 3 assets	$ 4	$ 2