Accrued Liabilities (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Accrued Liabilities [Abstract]
Salaries, benefits and related expenses	$ 349.8	$ 520.6
Office and related expenses	46.6	57.9
Acquisition obligations	15.1	43.7
Interest	39.0	40.3
Professional fees	21.8	25.3
Other	121.6	139.3
Total accrued liabilities	$ 593.9	$ 827.1