Segment Financial Information (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Statement [Line Items]
Premiums, revenues - external customers	$ 115,302us-gaap_PremiumsEarnedNet	$ 109,557us-gaap_PremiumsEarnedNet	$ 99,728us-gaap_PremiumsEarnedNet
Services, revenues - external customers	10,151us-gaap_SalesRevenueServicesNet	8,997us-gaap_SalesRevenueServicesNet	7,437us-gaap_SalesRevenueServicesNet
Products, revenues - external customers	4,242us-gaap_SalesRevenueGoodsNet	3,190us-gaap_SalesRevenueGoodsNet	2,773us-gaap_SalesRevenueGoodsNet
Investment and other income	779	745	680
Total revenues	130,474us-gaap_Revenues	122,489us-gaap_Revenues	110,618us-gaap_Revenues
Earnings from operations	10,274us-gaap_OperatingIncomeLoss	9,623us-gaap_OperatingIncomeLoss	9,254us-gaap_OperatingIncomeLoss
Interest expense	(618)us-gaap_InterestExpense	(708)us-gaap_InterestExpense	(632)us-gaap_InterestExpense
Earnings before income taxes	9,656	8,915	8,622
Total assets	86,382us-gaap_Assets	81,882us-gaap_Assets	80,885us-gaap_Assets
Purchases of property, equipment and capitalized software	1,525	1,307	1,070
Depreciation and amortization	1,478us-gaap_DepreciationAndAmortization	1,375us-gaap_DepreciationAndAmortization	1,309us-gaap_DepreciationAndAmortization
Optum [Member]
Statement [Line Items]
Investment and other income	145	128	114
Total revenues	47,746	38,117	30,399
Earnings from operations	3,282	2,491	1,567
Interest expense	0	0	0
Earnings before income taxes	3,282	2,491	1,567
Total assets	24,734	20,607	17,999
Purchases of property, equipment and capitalized software	752	637	688
Depreciation and amortization	706	609	674
External Customers [Member]
Statement [Line Items]
Premiums, revenues - external customers	115,302	109,557	99,728
Services, revenues - external customers	10,151	8,997	7,437
Products, revenues - external customers	4,242	3,190	2,773
Total revenues	129,695	121,744	109,938
External Customers [Member] \| Optum [Member]
Statement [Line Items]
Premiums, revenues - external customers	2,657	2,533	1,743
Services, revenues - external customers	3,635	2,921	2,657
Products, revenues - external customers	4,239	3,182	2,772
Total revenues	10,531	8,636	7,172
Intersegment [Member]
Statement [Line Items]
Total revenues	0	0	0
Intersegment [Member] \| Optum [Member]
Statement [Line Items]
Total revenues	37,070	29,353	23,113
Operating Segments [Member] \| UnitedHealthcare [Member]
Statement [Line Items]
Investment and other income	634	617	566
Total revenues	119,798	113,725	103,332
Earnings from operations	6,992	7,132	7,687
Interest expense	0	0	0
Earnings before income taxes	6,992	7,132	7,687
Total assets	62,405	61,942	62,971
Purchases of property, equipment and capitalized software	773	670	382
Depreciation and amortization	772	766	635
Operating Segments [Member] \| Optumhealth [Member]
Statement [Line Items]
Investment and other income	144	127	113
Total revenues	11,032	9,855	8,147
Earnings from operations	1,090	949	538
Interest expense	0	0	0
Earnings before income taxes	1,090	949	538
Total assets	11,148	9,244	8,198
Purchases of property, equipment and capitalized software	212	185	163
Depreciation and amortization	179	158	164
Operating Segments [Member] \| Optuminsight [Member]
Statement [Line Items]
Investment and other income	1	1	0
Total revenues	5,227	4,714	4,257
Earnings from operations	1,002	831	656
Interest expense	0	0	0
Earnings before income taxes	1,002	831	656
Total assets	8,112	6,880	6,367
Purchases of property, equipment and capitalized software	484	363	409
Depreciation and amortization	433	359	411
Operating Segments [Member] \| Optumrx [Member]
Statement [Line Items]
Investment and other income	0	0	1
Total revenues	31,976	24,006	18,359
Earnings from operations	1,190	711	373
Interest expense	0	0	0
Earnings before income taxes	1,190	711	373
Total assets	5,474	4,483	3,434
Purchases of property, equipment and capitalized software	56	89	116
Depreciation and amortization	94	92	99
Operating Segments [Member] \| External Customers [Member] \| UnitedHealthcare [Member]
Statement [Line Items]
Premiums, revenues - external customers	112,645	107,024	97,985
Services, revenues - external customers	6,516	6,076	4,780
Products, revenues - external customers	3	8	1
Total revenues	119,164	113,108	102,766
Operating Segments [Member] \| External Customers [Member] \| Optumhealth [Member]
Statement [Line Items]
Premiums, revenues - external customers	2,657	2,533	1,743
Services, revenues - external customers	1,300	819	767
Products, revenues - external customers	18	19	21
Total revenues	3,975	3,371	2,531
Operating Segments [Member] \| External Customers [Member] \| Optuminsight [Member]
Statement [Line Items]
Premiums, revenues - external customers	0	0	0
Services, revenues - external customers	2,224	2,006	1,807
Products, revenues - external customers	96	92	87
Total revenues	2,320	2,098	1,894
Operating Segments [Member] \| External Customers [Member] \| Optumrx [Member]
Statement [Line Items]
Premiums, revenues - external customers	0	0	0
Services, revenues - external customers	111	96	83
Products, revenues - external customers	4,125	3,071	2,664
Total revenues	4,236	3,167	2,747
Operating Segments [Member] \| Intersegment [Member] \| UnitedHealthcare [Member]
Statement [Line Items]
Total revenues	0	0	0
Operating Segments [Member] \| Intersegment [Member] \| Optumhealth [Member]
Statement [Line Items]
Total revenues	6,913	6,357	5,503
Operating Segments [Member] \| Intersegment [Member] \| Optuminsight [Member]
Statement [Line Items]
Total revenues	2,906	2,615	2,363
Operating Segments [Member] \| Intersegment [Member] \| Optumrx [Member]
Statement [Line Items]
Total revenues	27,740	20,839	15,611
Optum Eliminations [Member]
Statement [Line Items]
Investment and other income	0	0	0
Total revenues	(489)	(458)	(364)
Earnings from operations	0	0	0
Interest expense	0	0	0
Earnings before income taxes	0	0	0
Total assets	0	0	0
Purchases of property, equipment and capitalized software	0	0	0
Depreciation and amortization	0	0	0
Optum Eliminations [Member] \| External Customers [Member]
Statement [Line Items]
Premiums, revenues - external customers	0	0	0
Services, revenues - external customers	0	0	0
Products, revenues - external customers	0	0	0
Total revenues	0	0	0
Optum Eliminations [Member] \| Intersegment [Member]
Statement [Line Items]
Total revenues	(489)	(458)	(364)
Corporate and Eliminations [Member]
Statement [Line Items]
Investment and other income	0	0	0
Total revenues	(37,070)	(29,353)	(23,113)
Earnings from operations	0	0	0
Interest expense	(618)	(708)	(632)
Earnings before income taxes	(618)	(708)	(632)
Total assets	(757)	(667)	(85)
Purchases of property, equipment and capitalized software	0	0	0
Depreciation and amortization	0	0	0
Corporate and Eliminations [Member] \| External Customers [Member]
Statement [Line Items]
Premiums, revenues - external customers	0	0	0
Services, revenues - external customers	0	0	0
Products, revenues - external customers	0	0	0
Total revenues	0	0	0
Corporate and Eliminations [Member] \| Intersegment [Member]
Statement [Line Items]
Total revenues	$ (37,070)	$ (29,353)	$ (23,113)

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