Fair Value on a Recurring Basis (Details) - USD ($) $ in Millions		Dec. 31, 2016	Dec. 31, 2015
Level 1
Fair value assets and liabilities measured on recurring basis
Cash equivalents		$ 440.8	$ 875.7
Short-term marketable securities		3.0	6.8
Long-term investments		0.4	0.4
Fair value of total assets, recurring		$ 444.2	$ 882.9
Fair value of assets measured on a recurring basis, percentage of total assets		3.60%	7.00%
Contingent acquisition obligations	[1]	$ 0.0	$ 0.0
Level 2
Fair value assets and liabilities measured on recurring basis
Cash equivalents		0.0	0.0
Short-term marketable securities		0.0	0.0
Long-term investments		0.0	0.0
Fair value of total assets, recurring		$ 0.0	$ 0.0
Fair value of assets measured on a recurring basis, percentage of total assets		0.00%	0.00%
Contingent acquisition obligations	[1]	$ 0.0	$ 0.0
Level 3
Fair value assets and liabilities measured on recurring basis
Cash equivalents		0.0	0.0
Short-term marketable securities		0.0	0.0
Long-term investments		0.0	0.0
Fair value of total assets, recurring		$ 0.0	$ 0.0
Fair value of assets measured on a recurring basis, percentage of total assets		0.00%	0.00%
Contingent acquisition obligations	[1]	$ 205.4	$ 143.9
Fair Value, Total
Fair value assets and liabilities measured on recurring basis
Cash equivalents		440.8	875.7
Short-term marketable securities		3.0	6.8
Long-term investments		0.4	0.4
Fair value of total assets, recurring		$ 444.2	$ 882.9
Fair value of assets measured on a recurring basis, percentage of total assets		3.60%	7.00%
Contingent acquisition obligations	[1]	$ 205.4	$ 143.9

[1] Contingent acquisition obligations includes deferred acquisition payments and unconditional obligations to purchase additional noncontrolling equity shares of consolidated subsidiaries. Fair value measurement of the obligations is based upon actual and projected operating performance targets as specified in the related agreements. The increase in this balance of $61.5 from December 31, 2015 to December 31, 2016 is primarily due to acquisitions and exercised put options of $105.8, partially offset by payments of $65.1. The amounts payable within the next twelve months are classified in accrued liabilities; any amounts payable thereafter are classified in other non-current liabilities.