v3.8.0.1
Investments (Net Unrealized Gains Losses on Investments by Asset Class) (Details) - USD ($)
$ in Millions
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Gain (Loss) on Investments [Line Items]      
Net Unrealized Gains (Losses) on Investments $ 36,398 $ 32,732 $ 28,474
Fixed Maturities | Available-for-sale | OTTI      
Gain (Loss) on Investments [Line Items]      
Net Unrealized Gains (Losses) on Investments 286 312 234
Fixed Maturities | Available-for-sale | All Other      
Gain (Loss) on Investments [Line Items]      
Net Unrealized Gains (Losses) on Investments 34,109 28,526 24,673
Equity securities | Available-for-sale      
Gain (Loss) on Investments [Line Items]      
Net Unrealized Gains (Losses) on Investments 2,027 2,599 2,427
Derivatives designated as cash flow hedges      
Gain (Loss) on Investments [Line Items]      
Net Unrealized Gains (Losses) on Investments (39) 1,316 1,165
Other Investments      
Gain (Loss) on Investments [Line Items]      
Net Unrealized Gains (Losses) on Investments 15 $ (21) $ (25)
Other Investments | Held-to-maturity      
Gain (Loss) on Investments [Line Items]      
Net Unrealized Gains (Losses) on Investments $ 0