Investments (Credit Loss Rollforward) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Balance, beginning of period	$ 85	$ 128	$ 89	$ 138
Sales (maturities, pay downs or prepayments) of securities previously impaired as credit loss OTTI	(8)	(17)	(11)	(26)
Increase in cash flows — accretion of previous credit loss OTTI	0	0	(1)	(1)
Balance, end of period	$ 77	$ 111	$ 77	$ 111