Supplementary Data Accrued Liabilities (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Accrued Liabilities [Abstract]
Salaries, benefits and related expenses	$ 341.3	$ 499.0
Acquisition obligations	53.2	77.5
Office and related expenses	48.8	46.7
Interest	17.0	17.3
Other	90.4	153.5
Total accrued liabilities	$ 550.7	$ 794.0