Investments (Components of other-than-temporary impairment losses recognized in earnings) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Impairment losses recognized in earnings	$ 111	$ 44	$ 21
Corporate and other bonds
Debt Securities, Available-for-sale [Line Items]
Impairment losses recognized in earnings	87	33	12
Asset-backed
Debt Securities, Available-for-sale [Line Items]
Impairment losses recognized in earnings	$ 24	$ 11	$ 9