Earnings Per Share - Computation of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Basic:
Net earnings attributable to Black Knight	$ 40.3	$ 39.7	$ 404.9	$ 93.8
Shares used for basic net earnings per share:
Weighted average shares of common stock outstanding	154.5	155.4	154.4	155.5
Basic net earnings per share (in dollars per share)	$ 0.26	$ 0.26	$ 2.62	$ 0.60
Diluted:
Net earnings attributable to Black Knight	$ 40.3	$ 39.7	$ 404.9	$ 93.8
Shares used for diluted net earnings per share:
Weighted average shares of common stock outstanding	154.5	155.4	154.4	155.5
Dilutive effect of unvested restricted shares of common stock and OB PIUs	1.1	0.3	1.1	0.3
Weighted average shares of common stock, diluted	155.6	155.7	155.5	155.8
Diluted net earnings per share (in dollars per share)	$ 0.26	$ 0.25	$ 2.60	$ 0.60