Investments in Unconsolidated Affiliates - Summarized Financial Information (Details) - USD ($) $ in Millions	11 Months Ended	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Variable Interest Entity [Line Items]
Current assets		$ 352.1	$ 287.3
Total assets		6,350.9	6,090.5
Current liabilities, including short-term debt		264.8	291.3
Total liabilities		3,071.7	2,884.8
Total shareholders' equity	$ 1,898.5	2,090.4	2,627.7	$ 1,898.5	$ 1,786.5
Total liabilities, redeemable noncontrolling interests and shareholders' equity		6,350.9	6,090.5
Revenues		1,475.2	1,238.5	1,177.2
Income (loss) before provision for income taxes and equity in net income of affiliates		213.0	220.3	224.7
Net income (loss)		179.9	245.8	108.8
Net earnings attributable to Black Knight		207.9	264.1	$ 108.8
Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Current assets		718.0	874.4
Non-current assets		9,279.2	8,345.9
Total assets		9,997.2	9,220.3
Current liabilities, including short-term debt		1,004.9	828.1
Non-current liabilities		5,247.0	4,808.3
Total liabilities		6,251.9	5,636.4
Total shareholders' equity		3,745.3	3,583.9
Total liabilities, redeemable noncontrolling interests and shareholders' equity		9,997.2	9,220.3
Revenues	1,413.9	2,165.6	1,738.7
Income (loss) before provision for income taxes and equity in net income of affiliates	(540.0)	(45.2)	(226.4)
Net income (loss)	(425.8)	(65.9)	(111.6)
Net earnings attributable to Black Knight	$ (546.3)	$ (71.7)	$ (180.6)