Investments (Gains and Losses Recognized on Equity Securities) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Schedule of losses and gains related to equity securities [Line Items]
Net realized (losses) gains on financial instruments	$ (24)	$ 78
Equity Securities [Member]
Schedule of losses and gains related to equity securities [Line Items]
Net realized (losses) gains on financial instruments	(50)	79
Less: Net realized gains recognized on sale of equity securities during the period	(18)	(21)
Unrealized (losses) gains recognized on equity securities still held	$ (68)	$ 58