Fair Value Measurements (Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012		Mar. 31, 2012	Dec. 31, 2011
Financial instruments owned:
Mutual funds	$ 138	[1]	$ 139	[1]
Money market funds	22	[2]	483	[2]
Interest rate swap derivatives	5	[3]	6	[3]
Total assets measured at fair value	165		628
Fiduciary Assets:
State and local obligations (including non-U.S. locales)	2		3
Money market funds	107		149
Total fiduciary assets measured at fair value	109		152
Liabilities:
Contingent consideration liability	61	[4]	63	[4]
Senior Notes due 2014	255	[5]	256	[5]
Total liabilities measured at fair value	316		319
Identical Assets (Level 1) [Member]
Financial instruments owned:
Mutual funds	138	[1]	139	[1]
Money market funds	22	[2]	483	[2]
Interest rate swap derivatives	0		0
Total assets measured at fair value	160		622
Fiduciary Assets:
State and local obligations (including non-U.S. locales)	0		0
Money market funds	107		149
Total fiduciary assets measured at fair value	107		149
Liabilities:
Contingent consideration liability	0		0
Senior Notes due 2014	0		0
Total liabilities measured at fair value	0		0
Observable Inputs (Level 2) [Member]
Financial instruments owned:
Mutual funds	0		0
Money market funds	0		0
Interest rate swap derivatives	5	[3]	6	[3]
Total assets measured at fair value	5		6
Fiduciary Assets:
State and local obligations (including non-U.S. locales)	2		3
Money market funds	0		0
Total fiduciary assets measured at fair value	2		3
Liabilities:
Contingent consideration liability	0		0
Senior Notes due 2014	255	[5]	256	[5]
Total liabilities measured at fair value	255		256
Unobservable Inputs (Level 3) [Member]
Financial instruments owned:
Mutual funds	0		0
Money market funds	0		0
Interest rate swap derivatives	0		0
Total assets measured at fair value	0		0
Fiduciary Assets:
State and local obligations (including non-U.S. locales)	0		0
Money market funds	0		0
Total fiduciary assets measured at fair value	0		0
Liabilities:
Contingent consideration liability	61	[4]	63	[4]
Senior Notes due 2014	0		0
Total liabilities measured at fair value	61		63
Contingent Consideration [Member]
Liabilities:
Contingent consideration liability	$ 61		$ 63		$ 108	$ 110

[1] Included in other assets in the consolidated balance sheets.

[2] Included in cash and cash equivalents in the consolidated balance sheets.

[3] Included in other receivables in the consolidated balance sheets.

[4] Included in accounts payable and accrued liabilities and other liabilities in the consolidated balance sheets.

[5] Included in long term debt in the consolidated balance sheets.