Investments (Gains and Losses Recognized on Equity Securities) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Schedule of losses and gains related to equity securities [Line Items]
Net realized gains (losses) on financial instruments	$ 18	$ 11	$ (6)	$ 89
Equity Securities [Member]
Schedule of losses and gains related to equity securities [Line Items]
Net realized gains (losses) on financial instruments	45	13	(5)	92
Net realized (losses) gains recognized on sale of equity securities during the period	(13)	29	5	50
Unrealized (losses) gains recognized on equity securities still held	$ 58	$ (16)	$ (10)	$ 42