Accelerated Share Repurchases, Agreement Amount

No definition available.

Name:	hum_AcceleratedShareRepurchasesAgreementAmount
Namespace Prefix:	hum_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Common Stock Reclassified From Capital In Excess Of Par Value To Treasury Stock Upon Repurchase, Value

+ References

No definition available.

+ Details

Name:	hum_CommonStockReclassifiedFromCapitalInExcessOfParValueToTreasuryStockUponRepurchaseValue
Namespace Prefix:	hum_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Number of shares of common stock that were repurchased in the administration of our employee share-based compensation plans. Under the terms of these plans, we accept shares of common stock from option holders if they elect to surrender previously-owned shares upon exercise of the option to cover the exercise price of the options or, in the case of restricted shares of common stock, the withholding of shares to satisfy tax withholding obligations associated with the vesting of such shares.

+ References

No definition available.

+ Details

Name:	hum_ShareRepurchasesRelatedToEmployeeStockBasedCompensationAwardsShares
Namespace Prefix:	hum_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Cost of common stock that were repurchased in the administration of our employee share-based compensation plans. Under the terms of these plans, we accept shares of common stock from option holders if they elect to surrender previously-owned shares upon exercise of the option to cover the exercise price of the options or, in the case of restricted shares of common stock, the withholding of shares to satisfy tax withholding obligations associated with the vesting of such shares.

+ References

No definition available.

+ Details

Name:	hum_ShareRepurchasesRelatedToEmployeeStockBasedCompensationAwardsValue
Namespace Prefix:	hum_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Stock Repurchase Program, Remaining Authorized Repurchase Amount Expired Upon Replacement

+ References

No definition available.

+ Details

Name:	hum_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmountExpiredUponReplacement
Namespace Prefix:	hum_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Treasury Stock, Decrease In Capital In Excess Of Par Value

+ References

No definition available.

+ Details

Name:	hum_TreasuryStockDecreaseInCapitalInExcessOfParValue
Namespace Prefix:	hum_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Final price paid per share for the purchase of the targeted number of shares, determined by an average market price over a fixed period of time.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 30
-Section 25
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=6405686&loc=d3e22802-112653

+ Details

Name:	us-gaap_AcceleratedShareRepurchasesFinalPricePaidPerShare
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of cash receipt from (payment to) bank; or stock received from (issuance to) bank in the settlement of the accelerated share repurchase agreement.

+ References

+ Details

Name:	us-gaap_AcceleratedShareRepurchasesSettlementPaymentOrReceipt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- 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

Name:	us-gaap_EquityClassOfTreasuryStockLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of stock repurchase plan authorized.

+ References

No definition available.

+ Details

Name:	us-gaap_StockRepurchaseProgramAuthorizedAmount1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount remaining of a stock repurchase plan authorized.

+ References

No definition available.

+ Details

Name:	us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Number of shares that have been repurchased during the period and are being held in treasury.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21463-112644

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=120397183&loc=d3e187085-122770

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_TreasuryStockSharesAcquired
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Equity impact of the cost of common and preferred stock that were repurchased during the period. Recorded using the cost method.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21463-112644

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6405813&loc=d3e23239-112655

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=120397183&loc=d3e187085-122770

+ Details

Name:	us-gaap_TreasuryStockValueAcquiredCostMethod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_AcceleratedShareRepurchasesDateAxis=hum_July2019AcceleratedShareRepurchaseAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AcceleratedShareRepurchasesDateAxis=hum_December2020AcceleratedShareRepurchaseAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_CounterpartyNameAxis=hum_CitibankNAMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_CounterpartyNameAxis=hum_JPMorganChaseBankMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

STOCKHOLDERS' EQUITY - Narrative (Details) - USD ($) $ / shares in Units, shares in Thousands				3 Months Ended		5 Months Ended
	Dec. 23, 2020	Dec. 26, 2019	Aug. 02, 2019	Mar. 31, 2021	Mar. 31, 2020	Dec. 26, 2019	Apr. 27, 2021	Feb. 18, 2021	Dec. 22, 2020	Jul. 31, 2019	Jul. 30, 2019	Dec. 14, 2017
Equity, Class of Treasury Stock [Line Items]
Share repurchase authorization								$ 3,000,000,000			$ 3,000,000,000	$ 3,000,000,000
Remaining share repurchase authorization at replacement								$ 250,000,000			$ 1,030,000,000.00
Increase in treasury stock from stock repurchases				$ 30,000,000	$ 17,000,000
Common shares acquired in connection with employee stock plans (in shares)				80	40
Common shares acquired in connection with employee stock plans, amount				$ 30,000,000	$ 17,000,000
July 2019 ASR
Equity, Class of Treasury Stock [Line Items]
Accelerated stock repurchase agreement amount										$ 1,000,000,000
Accelerated stock repurchase payment			$ 1,000,000,000
Shares received (in shares)		700	2,700			3,400
Increase in treasury stock from stock repurchases			$ 800,000,000
Decrease in capital in excess of par value			$ 200,000,000
Average daily volume weighted-average share price of common stock during term of agreement (in dollars per share)						$ 296.19
Reclassification from capital in excess of par value to treasury stock		$ 200,000,000
December 2020 ASR
Equity, Class of Treasury Stock [Line Items]
Accelerated stock repurchase agreement amount									$ 1,750,000,000
Accelerated stock repurchase payment	$ 1,750,000,000
Shares received (in shares)	3,800
Increase in treasury stock from stock repurchases	$ 1,500,000,000
Decrease in capital in excess of par value	262,500,000
December 2020 ASR \| Citibank NA
Equity, Class of Treasury Stock [Line Items]
Accelerated stock repurchase payment	$ 875,000,000
Shares received (in shares)	1,900
December 2020 ASR \| JPMorgan Chase Bank
Equity, Class of Treasury Stock [Line Items]
Accelerated stock repurchase payment	$ 875,000,000
Shares received (in shares)	1,900
Subsequent event
Equity, Class of Treasury Stock [Line Items]
Remaining authorized amount							$ 3,000,000,000