Description of Business and Summary of Significant Accounting Policies - Narrative (Details)					1 Months Ended	2 Months Ended	12 Months Ended
	Sep. 11, 2020 USD ($)	Jul. 06, 2020 USD ($) $ / shares shares	Feb. 08, 2019 USD ($) shares	Aug. 08, 2018 USD ($) shares	Feb. 07, 2019 USD ($)	Mar. 31, 2019	Dec. 31, 2020 USD ($) segment $ / shares shares	Dec. 31, 2019 USD ($) $ / shares	Dec. 31, 2018 USD ($)
Class of Stock [Line Items]
Stock issued (shares) | shares		108,506,312
Common stock, par value (USD per share) | $ / shares							$ 0.0001	$ 0.0001
Consideration received on transaction		$ 2,381,000,000.0	$ 1,028,400,000	$ 1,028,400,000
Stock issued during period (shares) | shares							108,506,312
Syndication fee / issuance discount		$ 42,800,000	$ 21,600,000	$ 21,600,000
Number of reportable segments | segment							2
Initial term of long-term performance obligation contracts							10 years
Goodwill					$ 773,500,000		$ 2,856,200,000	$ 2,840,100,000	$ 770,800,000
Impairment charges related to goodwill and indefinite-lived intangibles					0		0	0	0
Other intangibles amortization expense					3,200,000		456,700,000	425,800,000
Foreign currency transaction losses					$ 800,000		$ 7,500,000	$ 15,800,000	2,200,000
Proportion of total units issued during fiscal year that are granted (as a percent)						94.00%
Other Intangibles
Class of Stock [Line Items]
Other intangibles amortization expense									$ 32,900,000
Minimum | Computer Software
Class of Stock [Line Items]
Useful lives of intangible assets							3 years
Minimum | Other Intangibles
Class of Stock [Line Items]
Useful lives of intangible assets							5 years
Maximum
Class of Stock [Line Items]
Term of lease							9 years
Maximum | Computer Software
Class of Stock [Line Items]
Useful lives of intangible assets							8 years
Maximum | Other Intangibles
Class of Stock [Line Items]
Useful lives of intangible assets							12 years
Arithmetic Average
Class of Stock [Line Items]
Term of lease							2 years
Buildings
Class of Stock [Line Items]
Useful lives of property, plant and equipment							40 years
Equipment | Minimum
Class of Stock [Line Items]
Useful lives of property, plant and equipment							3 years
Equipment | Maximum
Class of Stock [Line Items]
Useful lives of property, plant and equipment							10 years
Bridge Facility | Bridge Loan
Class of Stock [Line Items]
Term of debt instrument			364 days
Credit facility, maximum borrowing capacity			$ 63,000,000.0
New Senior Secured Notes | Secured Debt
Class of Stock [Line Items]
Face amount of debt instrument			$ 700,000,000.0
Interest rate on debt instrument (as a percent)			6.875%
New Senior Unsecured Notes | Unsecured Debt
Class of Stock [Line Items]
Face amount of debt instrument			$ 750,000,000.0
Interest rate on debt instrument (as a percent)			10.25%
Secured Debt | New Term Loan Facility
Class of Stock [Line Items]
Term of debt instrument			7 years
Credit facility, maximum borrowing capacity			$ 2,530,000,000.0
Revolving Credit Facility | New Revolving Facility
Class of Stock [Line Items]
Term of debt instrument	5 years		5 years
Credit facility, maximum borrowing capacity	$ 850,000,000		$ 400,000,000.0
Series A Preferred Stock
Class of Stock [Line Items]
Stock issued (shares) | shares			1,050,000	1,050,000
Class A Units | Star Parent, L.P.
Class of Stock [Line Items]
Consideration received on transaction				$ 2,048,400,000
Stock issued during period (shares) | shares				206,787.3617
Syndication fee / issuance discount				$ 19,500,000
Class B Units | Star Parent, L.P.
Class of Stock [Line Items]
Stock issued during period (shares) | shares				6,817.7428
Class C Units | Star Parent, L.P.
Class of Stock [Line Items]
Stock issued during period (shares) | shares				32,987.0078
IPO
Class of Stock [Line Items]
Stock issued (shares) | shares		90,047,612
Common stock, par value (USD per share) | $ / shares		$ 0.0001
Offering price (USD per share) | $ / shares		$ 22.00
Private Placement
Class of Stock [Line Items]
Stock issued (shares) | shares		18,458,700
Offering price (USD per share) | $ / shares		$ 21.67
Issuance price per share relative to IPO price per share (as a percent)		98.50%
Private Placement | Subsidiary of Cannae Holdings
Class of Stock [Line Items]
Consideration received on transaction		$ 200,000,000.0
Private Placement | Subsidiary of Black Knight
Class of Stock [Line Items]
Consideration received on transaction		100,000,000.0
Private Placement | Affiliate of CC Capital
Class of Stock [Line Items]
Consideration received on transaction		$ 100,000,000.0