Business Combinations - Acquisition Date Fair Value of Consideration Transferred (Details) - USD ($) $ in Millions	Oct. 09, 2019	Feb. 01, 2019	Feb. 01, 2020
Komiko
Business Acquisition [Line Items]
Cash	$ 8.3
Contingent earnout payments	0.2
Total purchase consideration	$ 8.5
Pre-Acquisition ZI
Business Acquisition [Line Items]
Cash		$ 667.3
Liability for equity award settlement		25.2
Portion of replacement awards attributable to pre-acquisition service		27.9
Other purchase consideration liabilities		6.5
Deferred consideration		33.2	$ 25.0
Total purchase consideration		$ 760.1