Contingent Acquisition Obligations (Details) $ in Millions	Dec. 31, 2017 USD ($)
Deferred acquisition payments
Business Acquisition, Contingent Consideration [Line Items]
Future contingent acquisition obligation due in 2018	$ 41.9
Future contingent acquisition obligation due in 2019	27.5
Future contingent acquisition obligation due in 2020	16.1
Future contingent acquisition obligation due in 2021	24.4
Future contingent acquisition obligation due in 2022	4.8
Future contingent acquisition obligation due thereafter	6.3
Future contingent acquisition obligation due, total	121.0
Redeemable noncontrolling interests and call options with affiliates
Business Acquisition, Contingent Consideration [Line Items]
Future contingent acquisition obligation due in 2018	37.1	[1]
Future contingent acquisition obligation due in 2019	26.4	[1]
Future contingent acquisition obligation due in 2020	62.9	[1]
Future contingent acquisition obligation due in 2021	10.3	[1]
Future contingent acquisition obligation due in 2022	6.6	[1]
Future contingent acquisition obligation due thereafter	4.1	[1]
Future contingent acquisition obligation due, total	147.4	[1]
Redeemable at noncontrolling equity owners discretion
Business Acquisition, Contingent Consideration [Line Items]
Future contingent acquisition obligation due in 2018	24.8
Total contingent acquisition payments
Business Acquisition, Contingent Consideration [Line Items]
Future contingent acquisition obligation due in 2018	79.0
Future contingent acquisition obligation due in 2019	53.9
Future contingent acquisition obligation due in 2020	79.0
Future contingent acquisition obligation due in 2021	34.7
Future contingent acquisition obligation due in 2022	11.4
Future contingent acquisition obligation due thereafter	10.4
Future contingent acquisition obligation due, total	$ 268.4

[1] We have entered into certain acquisitions that contain both redeemable noncontrolling interests and call options with similar terms and conditions. The estimated amounts listed would be paid in the event of exercise at the earliest exercise date. We have certain redeemable noncontrolling interests that are exercisable at the discretion of the noncontrolling equity owners as of December 31, 2017. These estimated payments of $24.8 are included within the total payments expected to be made in 2018, and will continue to be carried forward into 2019 or beyond until exercised or expired. Redeemable noncontrolling interests are included in the table at current exercise price payable in cash, not at applicable redemption value, in accordance with the authoritative guidance for classification and measurement of redeemable securities.