Share-Based Compensation (Narrative) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Weighting of historical volatility	90.00%
Weighting of implied volatility	10.00%
Weighted-average grant date fair value of restricted shares granted during the period	$ 32
Share-based compensation expense	$ 326	$ 334	$ 305
Share-based compensation expense, net of tax effects	278	220	202
Total unrecognized compensation cost related to share awards	449
Total unrecognized compensation cost related to share awards, weighted-average period (in years)	1.2
Income tax benefit realized from share-based award exercises	78	94	106
Discounted stock purchase price calculation	85.00%
Total deferrals related to non-qualified, unfunded deferred compensation plans	258	216
Stock Options and SARs
Shares available for future grants	63.4
Period that stock options and SARS may be exercised from the date of grant	10
Weighted-average grant date fair value of stock options and SARs granted during the period (per share)	$ 13	$ 10	$ 9
Total intrinsic value of stock options and SARs exercised during the period	164	282	244
Restricted Stock
Shares available for future grants	12.5
Weighted-average grant date fair value of restricted shares granted during the period	$ 32	$ 29	$ 34
Total fair value of restricted shares vested during the period	$ 99	$ 56	$ 17
Employee Stock Purchase Plan [Member]
Shares available for future grants	5.6
Stock purchased under ESPP	3.8	3.7	2.9
Restricted Stock \| Lower Limit
Range of period that restricted shares vest ratably	3
Restricted Stock \| Upper Limit
Range of period that restricted shares vest ratably	5
Lower Limit
Period that stock options and SARS vest	four
Upper Limit
Period that stock options and SARS vest	six

Discounted stock purchase price calculation

Name:	unh_DiscountedStockPurchasePriceCalculation
Namespace Prefix:	unh
Data Type:	us-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vesting Period

+ Details

Name:	unh_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestingPeriod
Namespace Prefix:	unh
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	duration

- Definition

Share-based compensation, exercise price range, exercisable options, contractual term.

+ Details

Name:	unh_ShareBasedCompensationExercisableOptionsContractualTerm
Namespace Prefix:	unh
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	duration

- Definition

Share-based compensation expense, net of tax effects.

+ Details

Name:	unh_ShareBasedCompensationNetOfTax
Namespace Prefix:	unh
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Weighting of historical volatility

+ Details

Name:	unh_WeightingOfHistoricalVolatility
Namespace Prefix:	unh
Data Type:	us-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Weighting of implied volatility

+ Details

Name:	unh_WeightingOfImpliedVolatility
Namespace Prefix:	unh
Data Type:	us-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The carrying amount of the liability as of the balance sheet date to an individual under a deferred compensation arrangement. This amount may be the result of periodic accruals made over the period of active employment, or reflect termination benefits resulting contractual terms or a death benefit.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 123R
-Paragraph 64, 65

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Accounting Principles Board Opinion (APB)
-Number 12
-Paragraph 6, 7

+ Details

Name:	us-gaap_DeferredCompensationArrangementWithIndividualRecordedLiability
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Disclosure of the aggregate tax benefit realized from the exercise of stock options and the conversion of similar instruments during the annual period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 123R
-Paragraph A240
-Subparagraph i

+ Details

Name:	us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitRealizedFromExerciseOfStockOptions
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

As of the latest balance-sheet date presented, the total compensation cost related to outstanding, nonvested share-based compensation awards not yet recognized (will be charged against earnings as services are performed or other vesting criteria are met).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 123R
-Paragraph A240
-Subparagraph h

+ Details

Name:	us-gaap_EmployeeServiceShareBasedCompensationUnrecognizedCompensationCostsOnNonvestedAwards
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The weighted average period over which unrecognized share-based compensation costs are expected to be reported.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 123R
-Paragraph A240
-Subparagraph h

+ Details

Name:	us-gaap_EmployeeServiceShareBasedCompensationUnrecognizedCompensationCostsOnNonvestedAwardsWeightedAveragePeriodOfRecognition
Namespace Prefix:	us-gaap
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	duration

- Definition

The aggregate amount of noncash, equity-based employee remuneration. This may include the value of stock options, amortization of restricted stock, and adjustment for officers compensation. As noncash, this element is an add back when calculating net cash generated by operating activities using the indirect method.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 95
-Paragraph 28

+ Details

Name:	us-gaap_ShareBasedCompensation
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Description of the period of time over which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, which may be expressed in a variety of ways (for example, in years, month and year).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 123R
-Paragraph A240
-Subparagraph a

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod
Namespace Prefix:	us-gaap
Data Type:	us-types:durationStringItemType
Balance Type:	na
Period Type:	duration

- Definition

The weighted average fair value at grant for nonvested share-based awards issued during the period on other than stock option plans (for example, phantom stock plan, stock appreciation rights plan, performance target plan).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 123R
-Paragraph A240
-Subparagraph b(2)(c)

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 123R
-Paragraph A240
-Subparagraph c(1)

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
Namespace Prefix:	us-gaap
Data Type:	us-types:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

The total fair value of share-based awards for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares, other instruments, or cash in accordance with the terms of the arrangement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 123R
-Paragraph A240
-Subparagraph c(2)

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The difference between the maximum number of shares authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares already issued upon exercise of options or other share-based awards under the plan, and 2) shares reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
Namespace Prefix:	us-gaap
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

The total accumulated difference between fair values of underlying shares on dates of exercise and exercise price on options which were exercised (or share units converted) into shares during the reporting period under the plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 123R
-Paragraph A240
-Subparagraph c(2)

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 123R
-Paragraph A240
-Subparagraph c(1)

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
Namespace Prefix:	us-gaap
Data Type:	us-types:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of shares issued during the period as a result of an employee stock purchase plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 29, 30
-Article 5

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Accounting Principles Board Opinion (APB)
-Number 12
-Paragraph 10

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 04
-Article 3

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 129
-Paragraph 5

+ Details

Name:	us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans
Namespace Prefix:	us-gaap
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration