Consolidated Statements of Changes in Equity (Deficit) - USD ($) $ in Millions	Total	Cumulative Effect, Period of Adoption, Adjustment	Common Stock Class A	Common Stock Class B	Common Stock Class C	Additional Paid-in Capital	Retained Earnings	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment	AOCI	Noncontrolling Interests	Pre-Acquisition ZI
Beginning balance, Stockholders' Equity at Dec. 31, 2018	$ (119.1)	$ (1.8)					$ (119.1)	$ (1.8)	$ 0.0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201602Member
Net income (loss)	$ (40.2)						(40.2)
Member distributions	(6.1)						(6.1)
Equity-based compensation	5.6						5.6
Ending balance, Stockholders' Equity at Mar. 31, 2019	(161.6)						(161.6)		0.0
Beginning balance, Stockholders' Equity at Dec. 31, 2018	(119.1)	$ (1.8)					(119.1)	$ (1.8)	0.0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(72.5)
Net income (loss) prior to Reorganization Transactions	72.5
Other comprehensive income (loss)	(7.2)
Ending balance, Stockholders' Equity at Sep. 30, 2019	(217.2)						(210.0)		(7.2)
Beginning balance, Stockholders' Equity at Mar. 31, 2019	(161.6)						(161.6)		0.0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(19.9)						(19.9)
Member distributions	(7.3)						(7.3)
Other comprehensive income (loss)	(5.9)								(5.9)
Repurchase outstanding equity / member units	(11.9)						(11.9)
Equity-based compensation	5.9						5.9
Ending balance, Stockholders' Equity at Jun. 30, 2019	(200.7)						(194.8)		(5.9)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(12.4)						(12.4)
Net income (loss) prior to Reorganization Transactions	12.4
Member distributions	(3.1)						(3.1)
Other comprehensive income (loss)	(1.3)								(1.3)
Repurchase outstanding equity / member units	(5.2)						(5.2)
Equity-based compensation	5.5						5.5
Ending balance, Stockholders' Equity at Sep. 30, 2019	(217.2)						(210.0)		(7.2)
Beginning balance, Members' Deficit at Dec. 31, 2019	(213.8)										$ (207.8)
Beginning balance, Stockholders' Equity (in shares) at Dec. 31, 2019			0	0	0
Beginning balance, Stockholders' Equity at Dec. 31, 2019	(213.8)		$ 0.0	$ 0.0	$ 0.0	$ 0.0	0.0		(6.0)	$ 0.0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(5.9)										(5.9)
Member distributions	(5.0)										(5.0)
Other comprehensive income (loss)	(6.7)								(6.7)
Equity-based compensation	11.3										11.3
Ending balance, Members' Deficit at Mar. 31, 2020											(207.4)
Ending balance, Stockholders' Equity (in shares) at Mar. 31, 2020			0	0	0
Ending balance, Stockholders' Equity at Mar. 31, 2020	(220.1)		$ 0.0	$ 0.0	$ 0.0	0.0	0.0		(12.7)	0.0
Beginning balance, Members' Deficit at Dec. 31, 2019	(213.8)										(207.8)
Beginning balance, Stockholders' Equity (in shares) at Dec. 31, 2019			0	0	0
Beginning balance, Stockholders' Equity at Dec. 31, 2019	(213.8)		$ 0.0	$ 0.0	$ 0.0	0.0	0.0		(6.0)	0.0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(72.7)
Net income (loss) prior to Reorganization Transactions	5.1
Other comprehensive income (loss)	(4.1)
Ending balance, Members' Deficit at Sep. 30, 2020											0.0
Ending balance, Stockholders' Equity (in shares) at Sep. 30, 2020			69,173,426	228,491,601	91,582,353
Ending balance, Stockholders' Equity at Sep. 30, 2020	820.5		$ 0.7	$ 2.3	$ 0.9	402.1	(29.5)		(2.9)	446.9
Beginning balance, Members' Deficit at Mar. 31, 2020											(207.4)
Beginning balance, Stockholders' Equity (in shares) at Mar. 31, 2020			0	0	0
Beginning balance, Stockholders' Equity at Mar. 31, 2020	(220.1)		$ 0.0	$ 0.0	$ 0.0	0.0	0.0		(12.7)	0.0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss) prior to Reorganization Transactions	0.8										0.8
Net income subsequent to Reorganization Transactions	(78.7)						(34.4)			(44.3)
Member distributions	(1.8)										(1.8)
Other comprehensive loss prior to Reorganization Transactions and IPO	(1.0)								(1.0)
Other comprehensive loss prior to Reorganization Transactions and IPO	4.5										4.5
Initial effect of the Reorganization Transactions and IPO on noncontrolling interests (in shares)				242,414,027	98,381,656
Initial effect of the Reorganization Transactions and IPO on noncontrolling interests				$ 2.4	$ 1.0	(628.1)			8.4	412.4	203.9
Issuance of Class A common stock in IPO, net of costs			48,528,783
Issuance of Class A common stock in IPO, net of costs	1,016.6		$ 0.5			1,016.1
Purchases of ZoomInfo OpCo units in connection with IPO (in shares)			2,370,948	(2,370,948)
Purchases of ZoomInfo OpCo units in connection with IPO	(47.2)					(47.2)
Purchases of Class C units in connection with IPO (in shares)			275,269		(275,269)
Purchases of Class C units in connection with IPO	(5.5)					(5.5)
Opco Units exchanged into Class A shares (in shares)			878,984	(878,984)
Opco Units exchanged into Class A shares	0.0
Forfeitures / cancellations (in shares)			(59,693)	(10,882)
Forfeitures / cancellations	0.0
Series A Preferred Unit redemption accretion	(74.0)					(74.0)
Increase in deferred tax asset from step-up in tax basis under TRA related to unit exchanges	126.3					82.0			1.4	42.9
Other comprehensive loss subsequent to Reorganization Transactions and IPO	3.4								1.1	2.3
Equity-based compensation subsequent to Reorganization Transactions	60.0					23.1				36.9
Ending balance, Members' Deficit at Jun. 30, 2020											0.0
Ending balance, Stockholders' Equity (in shares) at Jun. 30, 2020			51,994,291	239,153,213	98,106,387
Ending balance, Stockholders' Equity at Jun. 30, 2020	783.3		$ 0.5	$ 2.4	$ 1.0	366.4	(34.4)		(2.8)	450.2
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	11.1						4.9			6.2
Net income (loss) prior to Reorganization Transactions	0.0
Other comprehensive income (loss)	0.2								0.1	0.1
Paid and accrued tax distributions	(7.2)									(7.2)
Equity-based compensation	28.4					11.7				16.7
Exchanges (in shares)			17,179,135	(10,655,101)	(6,524,034)
Exchanges	0.0		$ 0.2	$ (0.1)	$ (0.1)	19.3			(0.2)	(19.1)
Forfeitures / cancellations (in shares)				(6,511)
Forfeitures / cancellations	0.0
Series A Preferred Unit redemption accretion						(74.0)
Tax receivable agreement adjustments	4.7					4.7				0.0
Ending balance, Members' Deficit at Sep. 30, 2020											$ 0.0
Ending balance, Stockholders' Equity (in shares) at Sep. 30, 2020			69,173,426	228,491,601	91,582,353
Ending balance, Stockholders' Equity at Sep. 30, 2020	$ 820.5		$ 0.7	$ 2.3	$ 0.9	$ 402.1	$ (29.5)		$ (2.9)	$ 446.9