Medical Claims Payable ((Favorable) Unfavorable Developments By Changes In Key Assumptions) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Medical Claims Payable [Abstract]
Assumed trend factors	$ (325)	$ (515)	$ (631)
Assumed completion factors	(175)	(415)	(502)
Total	$ (500)	$ (930)	$ (1,133)