Investments (Net Unrealized Gains Losses on Investments) (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Gain (Loss) on Securities [Line Items]
Net unrealized gains (losses) on investments	$ 43,371	$ 45,339
Fixed maturities | Available-for-sale | OTTI
Gain (Loss) on Securities [Line Items]
Net unrealized gains (losses) on investments		243
Fixed maturities | Available-for-sale | All Other
Gain (Loss) on Securities [Line Items]
Net unrealized gains (losses) on investments		44,279
Fixed maturities | Available-for-sale | With an allowance
Gain (Loss) on Securities [Line Items]
Net unrealized gains (losses) on investments	(118)
Fixed maturities | Available-for-sale | Without an allowance
Gain (Loss) on Securities [Line Items]
Net unrealized gains (losses) on investments	40,325
Derivatives designated as cash flow hedges
Gain (Loss) on Securities [Line Items]
Net unrealized gains (losses) on investments	3,186	832
Other investments
Gain (Loss) on Securities [Line Items]
Net unrealized gains (losses) on investments	(22)	$ (15)
Other investments | Held-to-maturity
Gain (Loss) on Securities [Line Items]
Net unrealized gains (losses) on investments	$ 0