Basis of Presentation - Additional Information (Details) $ in Millions	6 Months Ended
	Dec. 31, 2018 USD ($) group Segment	Jul. 01, 2018 USD ($)	Jun. 30, 2018 USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained earnings	$ 1,843.8		$ 1,727.0
Number of reportable segments | Segment	2
Number of client groups | group	4
Difference between Revenue Guidance in Effect before and after Topic 606 | ASU 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained earnings		$ 101.3
Accumulated Net Investment Gain (Loss) Including Portion Attributable to Noncontrolling Interest | ASU 2016-01
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of new accounting principle		$ (0.1)
Retained Earnings | ASU 2016-01
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of new accounting principle	$ 0.1