Other Intangible Assets (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	$ 614.1	$ 596.2
Accumulated amortization	(472.6)	(446.2)
Net carrying amount	141.5	150.0
Client relationships
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	603.8	587.1
Accumulated amortization	(467.1)	(441.4)
Net carrying amount	136.7	145.7
Other
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	10.3	9.1
Accumulated amortization	(5.5)	(4.8)
Net carrying amount	$ 4.8	$ 4.3