Consolidated Statements of Operations and Comprehensive Earnings - USD ($) shares in Millions, $ in Millions		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Statement [Abstract]
Revenues		$ 1,475.2	$ 1,238.5	$ 1,177.2
Expenses:
Operating expenses		793.9	669.6	646.0
Depreciation and amortization		365.0	270.7	236.2
Transition and integration costs		13.3	31.4	5.4
Total expenses		1,172.2	971.7	887.6
Operating income		303.0	266.8	289.6
Other income and expense:
Interest expense, net		(83.6)	(62.9)	(63.5)
Other (expense) income, net		(6.4)	16.4	(1.4)
Total other expense, net		(90.0)	(46.5)	(64.9)
Earnings before income taxes and equity in earnings (losses) of unconsolidated affiliates		213.0	220.3	224.7
Income tax expense		35.7	41.6	41.9
Earnings before equity in earnings (losses) of unconsolidated affiliates		177.3	178.7	182.8
Equity in earnings (losses) of unconsolidated affiliates, net of tax		2.6	67.1	(74.0)
Net earnings		179.9	245.8	108.8
Net losses attributable to redeemable noncontrolling interests		28.0	18.3
Net earnings attributable to Black Knight		207.9	264.1	108.8
Other comprehensive earnings (loss):
Unrealized holding gains (losses), net of tax(1)	[1]	1.7	(23.9)	(18.0)
Reclassification adjustments for losses included in net earnings, net of tax(2)	[2]	15.3	12.2
Total unrealized gains (losses) on interest rate swaps, net of tax		17.0	(11.7)	(18.0)
Foreign currency translation adjustment, net of tax (3)	[3]	(0.4)	(0.1)	(0.1)
Unrealized gains (losses) on investments in unconsolidated affiliates, net of tax(4)	[4]	4.7	(6.8)	(3.4)
Other comprehensive earnings (loss)		21.3	(18.6)	(21.5)
Comprehensive earnings		201.2	227.2	87.3
Net losses attributable to redeemable noncontrolling interests		28.0	18.3
Comprehensive earnings attributable to Black Knight		$ 229.2	$ 245.5	$ 87.3
Net earnings per share attributable to Black Knight common shareholders:
Basic		$ 1.34	$ 1.74	$ 0.74
Diluted		$ 1.33	$ 1.73	$ 0.73
Weighted average shares of common stock outstanding (see Note 5):
Basic		155.1	152.0	147.7
Diluted		155.8	152.9	148.6

[1] Net of income expense of $0.6 million and net of income tax benefit of $8.1 million and $6.1 million for the years ended December 31, 2021, 2020 and 2019, respectively.

[2] Amounts reclassified to net earnings relate to losses on interest rate swaps and are included in Interest expense, net above. Amounts are net of income tax benefit of $5.2 million and $4.1 million for the years ended December 31, 2021 and 2020, respectively.

[3] Net of income tax benefit of less than $0.1 million for the years ended December 31, 2021, 2020 and 2019.

[4] Net of income tax expense of $1.6 million and net of income tax benefit of $2.3 million and $1.1 million for the years ended December 31, 2021, 2020 and 2019, respectively