INVESTMENT SECURITIES - Realized Gains (Losses) Included Within Investment Income (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Investments, Debt and Equity Securities [Abstract]
Gross gains on investment securities	$ 46	$ 62	$ 219
Gross losses on investment securities	(101)	(144)	(8)
Gross gains on equity securities	1	51	23
Gross losses on equity securities	0	(174)	(364)
Net recognized losses on investment securities	$ (54)	$ (205)	$ (130)

Debt And Equity Securities, Realized Gain

No definition available.

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

- Definition

Debt And Equity Securities, Realized Loss

+ References

No definition available.

+ Details

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

- Definition

Amount of unrealized and realized gain (loss) on investment in debt and equity securities.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(7)(c))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483621/220-10-S99-2

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(9)(a))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483621/220-10-S99-2

+ Details

Name:	us-gaap_DebtAndEquitySecuritiesGainLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of realized gain from sale of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 321
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479536/321-10-50-4

+ Details

Name:	us-gaap_EquitySecuritiesFvNiRealizedGain
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of realized loss from sale of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

+ References

+ Details

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

- References

No definition available.

+ Details

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