Investments (Net Unrealized Gains Losses on Investments by Asset Class) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Gain (Loss) on Securities [Line Items]
Net Unrealized Gains (Losses) on Investments	$ 45,339	$ 22,720	$ 36,398
Fixed Maturities | Available-for-sale | OTTI
Gain (Loss) on Securities [Line Items]
Net Unrealized Gains (Losses) on Investments	243	190	286
Fixed Maturities | Available-for-sale | All Other
Gain (Loss) on Securities [Line Items]
Net Unrealized Gains (Losses) on Investments	44,279	21,721	34,109
Equity securities | Available-for-sale
Gain (Loss) on Securities [Line Items]
Net Unrealized Gains (Losses) on Investments	0	0	2,027
Derivatives designated as cash flow hedges
Gain (Loss) on Securities [Line Items]
Net Unrealized Gains (Losses) on Investments	832	811	(39)
Other Investments
Gain (Loss) on Securities [Line Items]
Net Unrealized Gains (Losses) on Investments	(15)	$ (2)	$ 15
Other Investments | Held-to-maturity
Gain (Loss) on Securities [Line Items]
Net Unrealized Gains (Losses) on Investments	$ 0