Dispositions (Income Statement Data) (Details) (USD $) In Millions, except Per Share data	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Revenue		$ 56		$ 381
Expense		52		345
Net operating income		4		36
Income Tax		1		16
Income from Kroll operations, net of tax		3		20
Other discontinued operations, net of tax		(4)		13
Disposals of discontinued operations	3	35	11	42
Income tax (credit) expense	1	(12)	(6)	(237)
Disposals of discontinued operations, net of tax	2	47	17	279
Discontinued operations net of tax	2	43	17	292
Discontinued operations, net of tax per basic share		$ 0.07	$ 0.03	$ 0.53
Discontinued operations, net of tax per diluted share	$ 0.01	$ 0.08	$ 0.03	$ 0.53
Other Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Other discontinued operations, net of tax		$ (7)		$ (7)