Organization (Details) medical_member in Millions	Sep. 30, 2020 medical_member states county
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of Medical Members \| medical_member	43
Number of counties in the Kansas City area the Company does not serve \| county	30
Number of states in which the Company is licensed to conduct insurance operations \| states	50

Number Of Counties In The State Of Kansas Company Does Not Serve

No definition available.

Name:	antm_NumberOfCountiesInStateOfKansasCompanyDoesNotServe
Namespace Prefix:	antm_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant