Investments (AFS contractual maturity) (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Amortized Cost
Due within one year	$ 619
Due after one year through five years	4,311
Due after five years through 10 years	2,258
Due after 10 years	3,951
Total having single maturity dates	11,139
Amortized cost	19,512
Fair Value
Due within one year	628
Due after one year through five years	4,572
Due after five years through 10 years	2,529
Due after 10 years	5,170
Total having single maturity dates	12,899
Total fair value	21,587
Residential mortgage backed securities [Member]
Amortized Cost
Without single maturity dates	3,213
Amortized cost	3,213	$ 3,039
Fair Value
Without single maturity dates	3,335
Total fair value	3,335	3,108
Commercial mortgage backed securities [Member]
Amortized Cost
Without single maturity dates	3,789
Amortized cost	3,789	3,526
Fair Value
Without single maturity dates	3,978
Total fair value	3,978	3,618
Asset backed securities [Member]
Amortized Cost
Without single maturity dates	1,371
Amortized cost	1,371	1,036
Fair Value
Without single maturity dates	1,375
Total fair value	$ 1,375	$ 1,080