Condensed Consolidated Statements of Earnings and Comprehensive Earnings - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Income Statement [Abstract]
Revenues	$ 394.5	$ 361.3	$ 781.7	$ 711.0
Expenses:
Operating expenses	216.8	197.0	424.7	383.2
Depreciation and amortization	92.5	90.4	184.0	178.2
Transition and integration costs	8.2	4.3	15.8	12.2
Total expenses	317.5	291.7	624.5	573.6
Operating income	77.0	69.6	157.2	137.4
Other income and expense:
Interest expense, net	(22.6)	(20.9)	(43.7)	(41.2)
Other expense, net	(2.4)	(1.0)	(3.6)	(4.2)
Total other expense, net	(25.0)	(21.9)	(47.3)	(45.4)
Earnings before income taxes and equity in (losses) earnings of unconsolidated affiliates	52.0	47.7	109.9	92.0
Income tax expense	11.6	10.5	10.5	15.7
Earnings before equity in (losses) earnings of unconsolidated affiliates	40.4	37.2	99.4	76.3
Equity in (losses) earnings of unconsolidated affiliates, net of tax	(0.1)	(5.0)	303.0	1.4
Net earnings	40.3	32.2	402.4	77.7
Net losses attributable to redeemable noncontrolling interests		7.5	2.5	16.1
Net earnings attributable to Black Knight	40.3	39.7	404.9	93.8
Other comprehensive earnings (loss):
Unrealized holding gains (losses), net of tax(1)	2.3	(0.2)	6.6	0.3
Reclassification adjustments for losses included in net earnings, net of tax(2)	2.0	4.0	5.2	7.9
Total unrealized gains on interest rate swaps, net of tax	4.3	3.8	11.8	8.2
Foreign currency translation adjustment, net of tax (3)	(0.4)	(0.1)	(0.6)	(0.4)
Unrealized gains (losses) on investments in unconsolidated affiliates, net of tax(4)	(2.4)	1.5	0.8	(1.6)
Other comprehensive earnings	1.5	5.2	12.0	6.2
Comprehensive earnings	41.8	37.4	414.4	83.9
Net losses attributable to redeemable noncontrolling interests		7.5	2.5	16.1
Comprehensive earnings attributable to Black Knight	$ 41.8	$ 44.9	$ 416.9	$ 100.0
Net earnings per share attributable to Black Knight common shareholders:
Basic	$ 0.26	$ 0.26	$ 2.62	$ 0.60
Diluted	$ 0.26	$ 0.25	$ 2.60	$ 0.60
Weighted average shares of common stock outstanding (see Note 5):
Basic	154.5	155.4	154.4	155.5
Diluted	155.6	155.7	155.5	155.8