Goodwill and Other Intangible Assets (Details) (USD $) In Millions	6 Months Ended
Jun. 30, 2011
Changes in the net carrying amount of goodwill by operating segment (in millions)
Balance at the beginning of the period	$ 8,647
Goodwill related to current year acquisitions	59
Goodwill related to disposals	(2)
Goodwill related to prior year acquisitions	17
Foreign currency revaluation and other	254
Balance at the end of the period	8,975
Risk Solutions
Changes in the net carrying amount of goodwill by operating segment (in millions)
Balance at the beginning of the period	5,549
Goodwill related to current year acquisitions	59
Goodwill related to disposals	(2)
Goodwill related to prior year acquisitions	(1)
Transfers	122
Foreign currency revaluation and other	232
Balance at the end of the period	5,959
HR Solutions
Changes in the net carrying amount of goodwill by operating segment (in millions)
Balance at the beginning of the period	3,098
Goodwill related to prior year acquisitions	18
Transfers	(122)
Foreign currency revaluation and other	22
Balance at the end of the period	$ 3,016

Represents the transfers during the reporting period taken place in the carrying value of goodwill.

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Balance Type:	debit
Period Type:	duration

- Definition

Net changes to the recorded value of goodwill for foreign currency translation adjustments.

+ Details

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- Definition

Carrying amount as of the balance sheet date, which is the cumulative amount paid, adjusted for any amortization recognized prior to adoption of FAS 142 and for any impairment charges, in excess of the fair value of net assets acquired in one or more business combination transactions.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 142
-Paragraph 43

+ Details

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Balance Type:	debit
Period Type:	instant

- Definition

The aggregate amount of goodwill acquired in the period and allocated to the reportable segment. The value is stated at fair value based on the purchase price allocation.

+ 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(1)

+ Details

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

- Definition

Purchase price allocation adjustment for allocation not yet complete at the prior year end.

+ Details

Name:	us-gaap_GoodwillAllocationAdjustment
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ Details

Name:	us-gaap_GoodwillRollForward
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Data Type:	xbrli:stringItemType
Balance Type:	na
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- Definition

Write-off of the carrying amount of goodwill associated with all or a portion of a reporting unit that is sold in the period.

+ 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(3)

+ Details

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Balance Type:	credit
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