Goodwill and Other Intangible Assets - Finite-Lived Intangible Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Finite Lived Intangible Asset Disclosures
Weighted average remaining expected life of finite lived intangible assets	15 years
Gross carrying amount	$ 782.9	$ 756.2
Accumulated amortization	277.7	228.7
Net carrying amount	505.2	527.5
Finite lived intangible assets fully amortized during the period	10.2	2.2	$ 0.5
Amortization expense for intangible assets with finite useful lives	45.4	$ 44.5	42.5
Estimated amortization expense for the next five years
Year 1: Finite lived intangible assets amortization	44.7
Year 2: Finite lived intangible assets amortization	43.5
Year 3: Finite lived intangible assets amortization	42.9
Year 4: Finite lived intangible assets amortization	40.4
Year 5: Finite lived intangible assets amortization	$ 39.7
Brazil mutual fund company
Finite Lived Intangible Asset Disclosures
Gross carrying amount			11.5
Accumulated amortization			3.2
Brazil mutual fund company | Operating expense
Finite Lived Intangible Asset Disclosures
Other finite lived intangible assets impairment			$ 8.3