Investments (OTTI rollforward) (Details 6) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
OTTI Credit Losses Recognized in Earnings Rollforward
Beginning balance	$ 2	$ 2	$ 2	$ 2
Credit losses for which an other-than-temporary impairment was previously recognized	0	0	0	0
Ending balance	$ 2	$ 2	$ 2	$ 2