Investments (Gains and Losses Recognized on Equity Securities) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule of losses and gains related to equity securities [Line Items]
Net realized gains (losses) on financial instruments	$ 114	$ (180)	$ 145
Equity Securities [Member]
Schedule of losses and gains related to equity securities [Line Items]
Net realized gains (losses) on financial instruments	63	(199)
Net realized gains (losses) recognized on equity securities sold during the period	39	(57)
Unrealized gains (losses) recognized in income on equity securities	$ 24	$ (142)