Investments (OTTI rollforward) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2020 USD ($)
OTTI Credit Losses Recognized in Earnings Rollforward
Beginning balance	$ 0	[1]
Additions for which credit losses were not previously recognized	13
Ending balance	$ 13

[1] Prior to January 1, 2020, credit losses on Available-for-Sale securities were not recorded in an allowance but were recorded as a reduction of the book value of the security if the security was other-than-temporarily impaired. There is no adoption impact due to the prospective transition for Available-for-Sale securities.