Accrued Liabilities (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Accrued Liabilities [Abstract]
Salaries, benefits and related expenses	$ 329.3	$ 478.2
Office and related expenses	50.3	51.6
Acquisition obligations	11.9	29.5
Interest	48.3	42.4
Professional fees	20.0	21.7
Other	88.8	104.8
Total accrued liabilities	$ 548.6	$ 728.2