Goodwill and Other Intangible Assets (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2014
Changes in the net carrying amount of goodwill by operating segment (in millions)
Beginning balance	$ 8,997
Goodwill related to current year acquisitions	4
Goodwill related to prior year acquisitions	(1)
Foreign currency translation	30
Ending balance	9,030
Risk Solutions [Member]
Changes in the net carrying amount of goodwill by operating segment (in millions)
Beginning balance	6,020
Goodwill related to current year acquisitions	2
Goodwill related to prior year acquisitions	(1)
Foreign currency translation	31
Ending balance	6,052
HR Solutions [Member]
Changes in the net carrying amount of goodwill by operating segment (in millions)
Beginning balance	2,977
Goodwill related to current year acquisitions	2
Goodwill related to prior year acquisitions	0
Foreign currency translation	(1)
Ending balance	$ 2,978

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=14024403&loc=d3e13816-109267

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266

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Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination.

+ References

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Amount of increase (decrease) from adjustments after acquisition date under purchase accounting of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (g)

-URI http://asc.fasb.org/extlink&oid=14024403&loc=d3e13816-109267

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 10

-Section 25

-Paragraph 16

-URI http://asc.fasb.org/extlink&oid=21917927&loc=d3e961-128460

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Amount of increase (decrease) from foreign currency translation adjustments of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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