Goodwill and Other Intangible Assets (Details) $ in Millions	9 Months Ended
Sep. 30, 2016 USD ($)
Changes in the net carrying amount of goodwill by operating segment
Beginning balance	$ 8,448
Goodwill related to current year acquisitions	117
Goodwill related to disposals	(33)
Goodwill related to prior year acquisitions	2
Foreign currency translation	(82)
Ending balance	8,452
Risk Solutions [Member]
Changes in the net carrying amount of goodwill by operating segment
Beginning balance	5,593
Goodwill related to current year acquisitions	112
Goodwill related to disposals	(7)
Goodwill related to prior year acquisitions	2
Foreign currency translation	(56)
Ending balance	5,644
HR Solutions [Member]
Changes in the net carrying amount of goodwill by operating segment
Beginning balance	2,855
Goodwill related to current year acquisitions	5
Goodwill related to disposals	(26)
Goodwill related to prior year acquisitions	0
Foreign currency translation	(26)
Ending balance	$ 2,808

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
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=35741047&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

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=64834752&loc=SL49117168-202975

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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 805
-SubTopic 10
-Section 25
-Paragraph 16
-URI http://asc.fasb.org/extlink&oid=73531572&loc=d3e961-128460

Reference 2: http://www.xbrl.org/2003/role/presentationRef
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-Topic 350
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-Section 50
-Paragraph 1
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

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