Goodwill and Other Intangible Assets (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Intangible assets with indefinite lives
Trademarks	$ 1,024		$ 1,024		$ 1,024
Intangible assets with finite lives
Intangible assets with finite lives, gross carrying amount	4,269		4,269		4,242
Intangible assets with finite lives, accumulated amortization	1,163		1,163		966
Intangible assets, net	3,106		3,106		3,276
Amortization expense on intangible assets	104	91	208	182
Estimated amortization for intangible assets
Remainder of 2012			213
2013			383
2014			331
2015			286
2016			242
Thereafter			627
Estimated future amortization for intangible assets			2,082
HR Solutions
Estimated amortization for intangible assets
Remainder of 2012			146
2013			275
2014			238
2015			208
2016			174
Thereafter			475
Estimated future amortization for intangible assets			1,516
Risk Solutions
Estimated amortization for intangible assets
Remainder of 2012			67
2013			108
2014			93
2015			78
2016			68
Thereafter			152
Estimated future amortization for intangible assets			566
Trademarks
Intangible assets with finite lives
Intangible assets with finite lives, gross carrying amount	4		4		4
Intangible assets with finite lives, accumulated amortization	2		2		1
Intangible assets, net	2		2		3
Customer Related and Contract Based
Intangible assets with finite lives
Intangible assets with finite lives, gross carrying amount	2,642		2,642		2,608
Intangible assets with finite lives, accumulated amortization	789		789		615
Intangible assets, net	1,853		1,853		1,993
Marketing, Technology and Other
Intangible assets with finite lives
Intangible assets with finite lives, gross carrying amount	599		599		606
Intangible assets with finite lives, accumulated amortization	372		372		350
Intangible assets, net	$ 227		$ 227		$ 256