Investments - Fixed Maturities by Contractual Maturity Periods (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Amortized Cost:
Due in one year or less	$ 1,323
Due after one year through five years	6,452
Due after five years through ten years	10,205
Due after ten years	4,064
Mortgage and other asset-backed securities	506
Amortized Cost	22,550	$ 21,867
Fair Value:
Due in one year or less	1,327
Due after one year through five years	6,522
Due after five years through ten years	9,992
Due after ten years	4,577
Mortgage and other asset-backed securities	510
Total fair value	$ 22,928