Discontinued Operations (Income Statement Data) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Discontinued Operations and Disposal Groups [Abstract]
Revenue	$ 0		$ 381		$ 699
Expense	0	[1]	345	[1]	958	[1]
Net operating income	0		36		(259)
Income Tax	0		16		24
Income from Kroll operations, net of tax	0		20		(283)
Other discontinued operations, net of tax	(17)		(7)		0
Income (loss) from discontinued operations, net of tax	(17)		13		(283)
Disposals of discontinued operations	25	[2]	58	[2]	8	[2]
Income tax (credit) expense	(25)	[3]	(235)	[3]	15	[3]
Disposals of discontinued operations, net of tax	50		293		(7)
Discontinued operations, net of tax	33		306		(290)
Discontinued operations, net of tax per basic share	$ 0.06		$ 0.55		$ (0.54)
Discontinued operations, net of tax per diluted share	$ 0.06		$ 0.55		$ (0.54)
Goodwill Impairment Charge From Discontinued Operations					$ 315

[1] Includes goodwill impairment charge of $315 million in 2009.

[2] Includes gain on sale of Kroll and the gain on the sale of KLS in 2010 and a loss on the sale of Kroll Government Services in 2009.

[3] Includes the provision /(credit) for income taxes relating to the recognition of tax benefits recorded in connection with the sale of Kroll as well as a tax provision of $36 million on the sale of KLS in 2010.