Equity Units Issued.

No definition available.

Name:	antm_EquityUnitsIssued1
Namespace Prefix:	antm_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

The amount of an increase authorized by an entity's Board of Directors to a previously authorized stock repurchase program.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Date the declared dividend will be paid, in CCYY-MM-DD format.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4304-108586

+ Details

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Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

The per share amount of a dividend declared, but not paid, as of the financial reporting date.

+ References

+ Details

Name:	us-gaap_DividendsPayableAmountPerShare
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Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Date the holder must own the stock to be entitled to the dividend, in CCYY-MM-DD format.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The cash inflow from the additional capital contribution to the entity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3255-108585

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Gross number of share options (or share units) granted during the period.

+ References

No definition available.

+ Details

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Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of new stock issued during the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
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-Name Accounting Standards Codification
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+ Details

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Balance Type:	na
Period Type:	duration

- Details

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Balance Type:
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- Details

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- Details

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- Details

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- Details

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Capital Stock (Narrative) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions			3 Months Ended						9 Months Ended
	Dec. 21, 2018	May 01, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Sep. 30, 2018	Sep. 30, 2017	Oct. 30, 2018	Dec. 07, 2017	May 12, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Dividends Payable, Date to be Paid			Sep. 25, 2018	Jun. 25, 2018	Mar. 23, 2018	Sep. 25, 2017	Jun. 23, 2017	Mar. 24, 2017
Dividends Payable, Date of Record			Sep. 10, 2018	Jun. 08, 2018	Mar. 09, 2018	Sep. 08, 2017	Jun. 09, 2017	Mar. 10, 2017
Increase In Stock Repurchase Program Authorization												$ 5,000
Issuance of common stock under Equity Units stock purchase contracts, shares									6.0
Proceeds from Issuance of Common Stock									$ 1,250	$ 0
Equity Unit Purchase Agreements [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Equity Units Issued													25.0
Equity Units, outstanding principal amount													$ 1,250
Issuance of common stock under Equity Units stock purchase contracts, shares		6.0
Proceeds from Issuance of Common Stock		$ 1,250
Subsequent Event [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Dividends Payable, Amount Per Share											$ 0.75
Dividends Payable, Date to be Paid	Dec. 21, 2018
Dividends Payable, Date of Record	Dec. 05, 2018
2018 to 2020 [Member] \| Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross									0.3
2015 to 2017 [Member] \| Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross									0.2