Investments Investments (Details) - Concentrations and Credit Quality - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Investment disclosure details
Fixed maturities, at fair value	$ 63,464	$ 62,694
Below investment grade [Member]
Investment disclosure details
Fixed maturities, at fair value	1,480	1,670
U.S. Treasury securities and obligations of U.S. government and government agencies and authorities [Member]
Investment disclosure details
Fixed maturities, at fair value	$ 2,064	$ 2,076
Credit Concentration Risk [Member] | Shareholders' equity, total [Member] | U.S. Treasury securities and obligations of U.S. government and government agencies and authorities [Member] | Minimum [Member]
Investment disclosure details
Concentration risk as a percentage of shareholders' equity	5.00%	5.00%