Investments Investments (Allowance for credit losses rollforward) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2020
Rollforward of the cumulative amounts recognized in the Consolidated Statements of Income for other-than-temporary impairments related to credit losses on securities
Beginning balance	$ 13	$ 0	[1]
Additions for which credit losses were not previously recognized	0	13
Ending balance	$ 13	$ 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.