Investments Investments (Schedule of Gains and Losses on Equity and Other Investments) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Gain (Loss) on Securities [Line Items]
Unrealized Gain (Loss) on Investments	$ 2,130	$ 3,088	$ (1,699)
Realized Investment Gains (Losses)	(498)	(530)	(652)
Equity Securities [Member]
Gain (Loss) on Securities [Line Items]
Equity Securities, FV-NI, Realized Gain (Loss)	586	104	(59)	[1]
Other Investments [Member]
Gain (Loss) on Securities [Line Items]
Realized Investment Gains (Losses)	(32)	(20)	(5)
Accounting Standards Update 2016-01 [Member] | Equity Securities [Member]
Gain (Loss) on Securities [Line Items]
Equity Securities, FV-NI, Realized Gain (Loss)	586	104	(59)
Unrealized Gain (Loss) on Investments	131	46	(129)
Gain (Loss) on Sale of Investments	455	58	70
Accounting Standards Update 2016-01 [Member] | Other Investments [Member]
Gain (Loss) on Securities [Line Items]
Unrealized Gain (Loss) on Investments	(32)	(15)	(126)
Gain (Loss) on Sale of Investments	0	(5)	121
Realized Investment Gains (Losses)	(32)	(20)	(5)
Accounting Standards Update 2016-01 [Member] | Equity securities and other investments [Member]
Gain (Loss) on Securities [Line Items]
Unrealized Gain (Loss) on Investments	99	31	(255)
Gain (Loss) on Sale of Investments	455	53	191
Realized Investment Gains (Losses)	$ 554	$ 84	$ (64)

[1] Relates to certain securities we intended to sell and securities written to market entering default.