Investments - Net appreciation (decline) recognized in net income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Debt and Equity Securities, FV-NI [Line Items]
Total	$ 728	$ 1,222
Equity securities
Debt and Equity Securities, FV-NI [Line Items]
Total	478	1,073
Limited partnership interests carried at fair value
Debt and Equity Securities, FV-NI [Line Items]
Total	$ 250	$ 149