Business Combinations - Narrative (Details) customer in Thousands, $ in Millions				3 Months Ended	6 Months Ended
	Feb. 01, 2021 USD ($)	Oct. 09, 2019 USD ($)	Feb. 01, 2019 USD ($) customer	Jun. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)	Feb. 01, 2020 USD ($)
Komiko
Business Acquisition [Line Items]
Value of consideration transferred		$ 8.5
Potential contingent payments		$ 4.0
Contingent payments attributable to purchase consideration (as a percent)		40.00%
Additional liability relating to contingent payments				$ 0.7	$ 1.7
Komiko | Developed technology
Business Acquisition [Line Items]
Identifiable finite-lived intangible assets		$ 2.4
Estimated useful life		7 years
Pre-Acquisition ZI
Business Acquisition [Line Items]
Value of consideration transferred			$ 760.1
Ownership acquired (as a percent)			100.00%
Number of customers served (over) | customer			8
Transaction costs incurred			$ 2.7
Cash acquired			12.1
Deferred consideration, current			$ 33.2			$ 25.0
Pre-Acquisition ZI | Cash Vesting Payment Program
Business Acquisition [Line Items]
Potential value of future payments				7.1	7.1
Contingent consideration expense				1.5	4.0
Pre-Acquisition ZI | Accrued expenses and other current liabilities
Business Acquisition [Line Items]
Deferred consideration, current				$ 9.8	$ 9.8
Pre-Acquisition ZI | Forecast
Business Acquisition [Line Items]
Agreements to pay deferred consideration	$ 10.0
Deferred consideration, noncurrent	$ 10.0
Pre-Acquisition ZI | Developed technology
Business Acquisition [Line Items]
Estimated useful life			5 years 9 months 18 days