Accrued Liabilities (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Accrued Liabilities [Abstract]
Salaries, benefits and related expenses	$ 478.2	$ 520.6
Office and related expenses	51.6	57.9
Acquisition obligations	29.5	43.7
Interest	42.4	40.3
Professional fees	21.7	25.3
Other	104.8	142.2
Total accrued liabilities	$ 728.2	$ 830.0