SEGMENT INFORMATION - Segment Results (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Segment Reporting Information [Line Items]
Premiums	$ 19,885	$ 18,904	$ 59,987	$ 55,822
Services revenue	845	457	1,802	1,331
Total external revenues	20,730	19,361	61,789	57,153
Total intersegment revenues	0	0	0	0
Investment income (loss)	(33)	714	221	940
Total revenues	20,697	20,075	62,010	58,093
Benefits	17,316	15,611	51,761	45,415
Operating costs	2,603	2,513	6,726	6,984
Depreciation and amortization	150	128	436	362
Total operating expenses	20,069	18,252	58,923	52,761
Income from operations	628	1,823	3,087	5,332
Interest expense	88	75	235	211
Other (income) expense, net	(1,096)	(7)	(562)	63
Income before income taxes and equity in net earnings	1,636	1,755	3,414	5,058
Equity in net earnings	15	35	69	68
Segment earnings (loss)	1,651	1,790	3,483	5,126
Less: noncontrolling interests	0	0	0	0
Segment earnings (loss) attributable to Humana	1,651	1,790	3,483	5,126
Individual Medicare Advantage
Segment Reporting Information [Line Items]
Premiums	14,642	12,949	44,042	38,748
Group Medicare Advantage
Segment Reporting Information [Line Items]
Premiums	1,737	1,880	5,267	5,867
Medicare stand-alone PDP
Segment Reporting Information [Line Items]
Premiums	541	622	1,867	2,108
Total Medicare
Segment Reporting Information [Line Items]
Premiums	16,920	15,451	51,176	46,723
Fully-insured
Segment Reporting Information [Line Items]
Premiums	1,237	1,948	3,774	4,717
Specialty
Segment Reporting Information [Line Items]
Premiums	432	424	1,298	1,278
Medicaid and other
Segment Reporting Information [Line Items]
Premiums	1,296	1,081	3,739	3,104
Home solutions
Segment Reporting Information [Line Items]
Services revenue	374	26	423	80
Provider
Segment Reporting Information [Line Items]
Services revenue	110	81	298	236
ASO and other
Segment Reporting Information [Line Items]
Services revenue	198	193	599	590
Pharmacy
Segment Reporting Information [Line Items]
Services revenue	163	157	482	425
Services
Segment Reporting Information [Line Items]
Total intersegment revenues	0	0	0	0
Products
Segment Reporting Information [Line Items]
Total intersegment revenues	0	0	0	0
Operating segments | Retail
Segment Reporting Information [Line Items]
Premiums	18,401	16,709	55,460	50,336
Services revenue	0	4	17	14
Total external revenues	18,401	16,713	55,477	50,350
Total intersegment revenues	1	0	1	0
Investment income (loss)	38	28	155	114
Total revenues	18,440	16,741	55,633	50,464
Benefits	16,207	14,224	48,574	41,939
Operating costs	1,669	1,877	4,653	5,047
Depreciation and amortization	108	87	320	251
Total operating expenses	17,984	16,188	53,547	47,237
Income from operations	456	553	2,086	3,227
Interest expense	0	0	0	0
Other (income) expense, net	0	0	0	0
Income before income taxes and equity in net earnings	456	553	2,086	3,227
Equity in net earnings	0	0	0	0
Segment earnings (loss)	456	553	2,086	3,227
Less: noncontrolling interests	0	0	0	0
Segment earnings (loss) attributable to Humana	456	553	2,086	3,227
Operating segments | Retail | Individual Medicare Advantage
Segment Reporting Information [Line Items]
Premiums	14,642	12,949	44,042	38,748
Operating segments | Retail | Group Medicare Advantage
Segment Reporting Information [Line Items]
Premiums	1,737	1,880	5,267	5,867
Operating segments | Retail | Medicare stand-alone PDP
Segment Reporting Information [Line Items]
Premiums	541	622	1,867	2,108
Operating segments | Retail | Total Medicare
Segment Reporting Information [Line Items]
Premiums	16,920	15,451	51,176	46,723
Operating segments | Retail | Fully-insured
Segment Reporting Information [Line Items]
Premiums	185	177	545	509
Operating segments | Retail | Specialty
Segment Reporting Information [Line Items]
Premiums	0	0	0	0
Operating segments | Retail | Medicaid and other
Segment Reporting Information [Line Items]
Premiums	1,296	1,081	3,739	3,104
Operating segments | Retail | Home solutions
Segment Reporting Information [Line Items]
Services revenue	0	0	0	0
Operating segments | Retail | Provider
Segment Reporting Information [Line Items]
Services revenue	0	0	0	0
Operating segments | Retail | ASO and other
Segment Reporting Information [Line Items]
Services revenue	0	4	17	14
Operating segments | Retail | Pharmacy
Segment Reporting Information [Line Items]
Services revenue	0	0	0	0
Operating segments | Retail | Services
Segment Reporting Information [Line Items]
Total intersegment revenues	1	0	1	0
Operating segments | Retail | Products
Segment Reporting Information [Line Items]
Total intersegment revenues	0	0	0	0
Operating segments | Group and Specialty
Segment Reporting Information [Line Items]
Premiums	1,484	1,593	4,527	4,884
Services revenue	198	189	582	576
Total external revenues	1,682	1,782	5,109	5,460
Total intersegment revenues	10	9	30	22
Investment income (loss)	3	3	11	12
Total revenues	1,695	1,794	5,150	5,494
Benefits	1,282	1,481	3,674	3,886
Operating costs	421	452	1,227	1,316
Depreciation and amortization	20	21	63	60
Total operating expenses	1,723	1,954	4,964	5,262
Income from operations	(28)	(160)	186	232
Interest expense	0	0	0	0
Other (income) expense, net	0	0	0	0
Income before income taxes and equity in net earnings	(28)	(160)	186	232
Equity in net earnings	0	0	0	0
Segment earnings (loss)	(28)	(160)	186	232
Less: noncontrolling interests	0	0	0	0
Segment earnings (loss) attributable to Humana	(28)	(160)	186	232
Operating segments | Group and Specialty | Individual Medicare Advantage
Segment Reporting Information [Line Items]
Premiums	0	0	0	0
Operating segments | Group and Specialty | Group Medicare Advantage
Segment Reporting Information [Line Items]
Premiums	0	0	0	0
Operating segments | Group and Specialty | Medicare stand-alone PDP
Segment Reporting Information [Line Items]
Premiums	0	0	0	0
Operating segments | Group and Specialty | Total Medicare
Segment Reporting Information [Line Items]
Premiums	0	0	0	0
Operating segments | Group and Specialty | Fully-insured
Segment Reporting Information [Line Items]
Premiums	1,052	1,169	3,229	3,606
Operating segments | Group and Specialty | Specialty
Segment Reporting Information [Line Items]
Premiums	432	424	1,298	1,278
Operating segments | Group and Specialty | Medicaid and other
Segment Reporting Information [Line Items]
Premiums	0	0	0	0
Operating segments | Group and Specialty | Home solutions
Segment Reporting Information [Line Items]
Services revenue	0	0	0	0
Operating segments | Group and Specialty | Provider
Segment Reporting Information [Line Items]
Services revenue	0	0	0	0
Operating segments | Group and Specialty | ASO and other
Segment Reporting Information [Line Items]
Services revenue	198	189	582	576
Operating segments | Group and Specialty | Pharmacy
Segment Reporting Information [Line Items]
Services revenue	0	0	0	0
Operating segments | Group and Specialty | Services
Segment Reporting Information [Line Items]
Total intersegment revenues	10	9	30	22
Operating segments | Group and Specialty | Products
Segment Reporting Information [Line Items]
Total intersegment revenues	0	0	0	0
Operating segments | Healthcare Services
Segment Reporting Information [Line Items]
Premiums	0	0	0	0
Services revenue	647	264	1,203	741
Total external revenues	647	264	1,203	741
Total intersegment revenues	7,390	6,865	21,554	20,414
Investment income (loss)	1	2	3	2
Total revenues	8,038	7,131	22,760	21,157
Benefits	0	0	0	0
Operating costs	7,634	6,871	21,749	20,274
Depreciation and amortization	46	46	127	135
Total operating expenses	7,680	6,917	21,876	20,409
Income from operations	358	214	884	748
Interest expense	0	0	0	0
Other (income) expense, net	0	0	0	0
Income before income taxes and equity in net earnings	358	214	884	748
Equity in net earnings	15	35	69	68
Segment earnings (loss)	373	249	953	816
Less: noncontrolling interests	0	0	0	0
Segment earnings (loss) attributable to Humana	373	249	953	816
Operating segments | Healthcare Services | Individual Medicare Advantage
Segment Reporting Information [Line Items]
Premiums	0	0	0	0
Operating segments | Healthcare Services | Group Medicare Advantage
Segment Reporting Information [Line Items]
Premiums	0	0	0	0
Operating segments | Healthcare Services | Medicare stand-alone PDP
Segment Reporting Information [Line Items]
Premiums	0	0	0	0
Operating segments | Healthcare Services | Total Medicare
Segment Reporting Information [Line Items]
Premiums	0	0	0	0
Operating segments | Healthcare Services | Fully-insured
Segment Reporting Information [Line Items]
Premiums	0	0	0	0
Operating segments | Healthcare Services | Specialty
Segment Reporting Information [Line Items]
Premiums	0	0	0	0
Operating segments | Healthcare Services | Medicaid and other
Segment Reporting Information [Line Items]
Premiums	0	0	0	0
Operating segments | Healthcare Services | Home solutions
Segment Reporting Information [Line Items]
Services revenue	374	26	423	80
Operating segments | Healthcare Services | Provider
Segment Reporting Information [Line Items]
Services revenue	110	81	298	236
Operating segments | Healthcare Services | ASO and other
Segment Reporting Information [Line Items]
Services revenue	0	0	0	0
Operating segments | Healthcare Services | Pharmacy
Segment Reporting Information [Line Items]
Services revenue	163	157	482	425
Operating segments | Healthcare Services | Services
Segment Reporting Information [Line Items]
Total intersegment revenues	5,087	4,852	14,838	14,514
Operating segments | Healthcare Services | Products
Segment Reporting Information [Line Items]
Total intersegment revenues	2,303	2,013	6,716	5,900
Eliminations/ Corporate
Segment Reporting Information [Line Items]
Premiums	0	602	0	602
Services revenue	0	0	0	0
Total external revenues	0	602	0	602
Total intersegment revenues	(7,401)	(6,874)	(21,585)	(20,436)
Investment income (loss)	(75)	681	52	812
Total revenues	(7,476)	(5,591)	(21,533)	(19,022)
Benefits	(173)	(94)	(487)	(410)
Operating costs	(7,121)	(6,687)	(20,903)	(19,653)
Depreciation and amortization	(24)	(26)	(74)	(84)
Total operating expenses	(7,318)	(6,807)	(21,464)	(20,147)
Income from operations	(158)	1,216	(69)	1,125
Interest expense	88	75	235	211
Other (income) expense, net	(1,096)	(7)	(562)	63
Income before income taxes and equity in net earnings	850	1,148	258	851
Equity in net earnings	0	0	0	0
Segment earnings (loss)	850	1,148	258	851
Less: noncontrolling interests	0	0	0	0
Segment earnings (loss) attributable to Humana	850	1,148	258	851
Eliminations/ Corporate | Individual Medicare Advantage
Segment Reporting Information [Line Items]
Premiums	0	0	0	0
Eliminations/ Corporate | Group Medicare Advantage
Segment Reporting Information [Line Items]
Premiums	0	0	0	0
Eliminations/ Corporate | Medicare stand-alone PDP
Segment Reporting Information [Line Items]
Premiums	0	0	0	0
Eliminations/ Corporate | Total Medicare
Segment Reporting Information [Line Items]
Premiums	0	0	0	0
Eliminations/ Corporate | Fully-insured
Segment Reporting Information [Line Items]
Premiums	0	602	0	602
Eliminations/ Corporate | Specialty
Segment Reporting Information [Line Items]
Premiums	0	0	0	0
Eliminations/ Corporate | Medicaid and other
Segment Reporting Information [Line Items]
Premiums	0	0	0	0
Eliminations/ Corporate | Home solutions
Segment Reporting Information [Line Items]
Services revenue	0	0	0	0
Eliminations/ Corporate | Provider
Segment Reporting Information [Line Items]
Services revenue	0	0	0	0
Eliminations/ Corporate | ASO and other
Segment Reporting Information [Line Items]
Services revenue	0	0	0	0
Eliminations/ Corporate | Pharmacy
Segment Reporting Information [Line Items]
Services revenue	0	0	0	0
Eliminations/ Corporate | Services
Segment Reporting Information [Line Items]
Total intersegment revenues	(5,098)	(4,861)	(14,869)	(14,536)
Eliminations/ Corporate | Products
Segment Reporting Information [Line Items]
Total intersegment revenues	$ (2,303)	$ (2,013)	$ (6,716)	$ (5,900)