Basis of Presentation, Use of Estimates and Significant Accounting Policies (Narrative) (Details) (USD $)	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Checks outstanding in excess of bank deposits		$ 1,300,000,000	$ 1,200,000,000
Goodwill impairment charge		172,000,000
Reinsurance receivable		2,000,000,000	2,000,000,000
Initial coverage limit		2,840,000,000	2,830,000,000
Catastrophic coverage		6,448,000,000	6,440,000,000
Annual out-of-pocket maximum	4,550,000,000
Catastrophic reinsurance subsidy coverage rate		80.00%
Variance of risk share		5.00%
Other Current Receivables [Member]
Reinsurance receivable included in other current receivables		126,000,000	139,000,000
Other Assets
Reinsurance receivable included in other assets		$ 1,900,000,000	$ 1,900,000,000

Catastrophic reinsurance subsidy coverage.

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- Definition

Carrying value as of the balance sheet date of bank checks outstanding in excess of bank deposits.

+ Details

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

- Definition

Medicare Part D annual out of pocket maximum.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Medicare Part D catastrophic coverage.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Medicare Part D initial coverage limit.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The current portion of the known and estimated amount recoverable as of the balance sheet date from reinsurers for claims paid or incurred by the ceding insurer and associated claims settlement expenses, including estimated amounts for claims incurred but not reported, and policy benefits, net of any related valuation allowance.

+ Details

Name:	unh_ReinsuranceRecoverablesCurrent
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The non-current portion of the known and estimated amount recoverable as of the balance sheet date from reinsurers for claims paid or incurred by the ceding insurer and associated claims settlement expenses, including estimated amounts for claims incurred but not reported, and policy benefits, net of any related valuation allowance.

+ Details

Name:	unh_ReinsuranceRecoverablesNoncurrent
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Data Type:	xbrli:monetaryItemType
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Period Type:	instant

- Definition

Variance Of Risk Share

+ Details

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Period Type:	duration

- Definition

Loss recognized during the period that results from the write-down of goodwill after comparing the implied fair value of reporting unit goodwill with the carrying amount of that goodwill. Goodwill is assessed at least annually for impairment.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 142
-Paragraph 45
-Subparagraph e(2)

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 142
-Paragraph 43

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 142
-Paragraph 47
-Subparagraph b

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 142
-Paragraph 20

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The known and estimated amount recoverable as of the balance sheet date from reinsurers for claims paid or incurred by the ceding insurer and associated claims settlement expenses, including estimated amounts for claims incurred but not reported, and policy benefits, net of any related valuation allowance.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 03
-Paragraph 6
-Article 7

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 113
-Paragraph 14, 16, 27, 113

+ Details

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Balance Type:	debit
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