Accrued Liabilities (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Accrued Liabilities [Abstract]
Salaries, benefits and related expenses	$ 402.1	$ 520.6
Office and related expenses	49.7	57.9
Acquisition obligations	45.5	43.7
Interest	24.7	40.3
Professional fees	22.6	25.3
Other	132.1	139.3
Total accrued liabilities	$ 676.7	$ 827.1