Investments (Credit Loss Rollforward) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Balance at January 1,	$ 89	$ 138
Reductions:
Sales (maturities, pay downs or prepayments) of securities previously impaired as credit loss OTTI	(47)	(48)
Increase in cash flows — accretion of previous credit loss OTTI	(2)	(1)
Balance at December 31,	$ 138	$ 187