Segment Information - Summary of Financial Information Concerning Reportable Segments (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 15, 2020	Dec. 31, 2019
Segment Reporting Information [Line Items]
Revenues from external customers	$ 139.7	$ 257.0	$ 415.3	$ 791.5
Interest, investment and other income, including recognized gains and losses, net	194.3	94.2	1,698.0	183.3
Total revenues and other income	334.0	351.2	2,113.3	974.8
Depreciation and amortization	6.5	9.5	22.2	29.8
Interest expense	(1.6)	(5.2)	(6.4)	(14.4)
(Loss) earnings before income taxes and equity in earnings (losses) of unconsolidated affiliates	164.3	67.5	1,564.2	114.9
Income tax (benefit) expense	35.1	15.1	335.6	16.2
(Loss) earnings before equity in earnings of unconsolidated affiliates	129.2	52.4	1,228.6	98.7
Equity in earnings (losses) of unconsolidated affiliates	(1.2)	(8.3)	3.6	(50.8)
Net (loss) earnings from continuing operations	128.0	44.1	1,232.2	47.9
Assets	3,868.6	1,893.7	3,868.6	1,893.7	$ 2,000.0	$ 2,092.2
Goodwill	53.5	76.5	53.5	76.5		66.1
Dun & Bradstreet and Optimal Blue Elimination
Segment Reporting Information [Line Items]
Revenues from external customers	(448.8)	(408.2)	(1,264.7)	(981.2)
Interest, investment and other income, including recognized gains and losses, net	9.3	(6.8)	41.5	(20.7)
Total revenues and other income	(439.5)	(415.0)	(1,223.2)	(1,001.9)
Depreciation and amortization	(139.7)	(123.3)	(406.6)	(340.6)
Interest expense	62.2	85.6	223.2	220.6
(Loss) earnings before income taxes and equity in earnings (losses) of unconsolidated affiliates	46.6	79.8	249.5	278.1
Income tax (benefit) expense	5.9	24.0	107.7	77.5
(Loss) earnings before equity in earnings of unconsolidated affiliates	40.7	55.8	141.8	200.6
Equity in earnings (losses) of unconsolidated affiliates	(8.5)	(9.2)	(55.1)	(55.3)
Net (loss) earnings from continuing operations	32.2	46.6	86.7	145.3
Assets	(11,185.4)	(9,075.7)	(11,185.4)	(9,075.7)
Goodwill	(4,094.9)	(2,967.4)	(4,094.9)	(2,967.4)
Restaurant revenue
Segment Reporting Information [Line Items]
Revenues from external customers	129.4	247.7	398.7	772.0
Restaurant revenue | Dun & Bradstreet and Optimal Blue Elimination
Segment Reporting Information [Line Items]
Revenues from external customers	0.0	0.0	0.0	0.0
Other operating revenue
Segment Reporting Information [Line Items]
Revenues from external customers	10.3	9.3	16.6	19.5
Other operating revenue | Dun & Bradstreet and Optimal Blue Elimination
Segment Reporting Information [Line Items]
Revenues from external customers	(448.8)	(408.2)	(1,264.7)	(981.2)
Restaurant Group
Segment Reporting Information [Line Items]
Revenues from external customers	129.4	247.7	398.7	772.0
Goodwill	53.5		53.5			66.1
Restaurant Group | Operating Segments
Segment Reporting Information [Line Items]
Revenues from external customers	129.4	247.7	398.7	772.0
Interest, investment and other income, including recognized gains and losses, net	1.5	1.1	9.2	4.6
Total revenues and other income	130.9	248.8	407.9	776.6
Depreciation and amortization	5.7	9.0	20.0	28.1
Interest expense	(1.7)	(1.5)	(5.9)	(4.0)
(Loss) earnings before income taxes and equity in earnings (losses) of unconsolidated affiliates	(14.2)	(13.2)	(59.1)	(32.9)
Income tax (benefit) expense	0.0	0.0	0.0	(0.1)
(Loss) earnings before equity in earnings of unconsolidated affiliates	(14.2)	(13.2)	(59.1)	(32.8)
Equity in earnings (losses) of unconsolidated affiliates	(0.1)	0.0	(15.0)	0.0
Net (loss) earnings from continuing operations	(14.3)	(13.2)	(74.1)	(32.8)
Assets	394.1	610.1	394.1	610.1
Goodwill	53.5	76.5	53.5	76.5
Restaurant Group | Restaurant revenue
Segment Reporting Information [Line Items]
Revenues from external customers	129.2	228.9	395.5	721.9
Restaurant Group | Restaurant revenue | Operating Segments
Segment Reporting Information [Line Items]
Revenues from external customers	129.4	247.7	398.7	772.0
Restaurant Group | Other operating revenue | Operating Segments
Segment Reporting Information [Line Items]
Revenues from external customers	0.0	0.0	0.0	0.0
Dun & Bradstreet | Operating Segments
Segment Reporting Information [Line Items]
Revenues from external customers	442.1	408.2	1,258.0	981.2
Interest, investment and other income, including recognized gains and losses, net	(9.3)	6.8	(41.5)	20.7
Total revenues and other income	432.8	415.0	1,216.5	1,001.9
Depreciation and amortization	134.1	123.3	401.0	340.6
Interest expense	(60.8)	(85.6)	(221.8)	(220.6)
(Loss) earnings before income taxes and equity in earnings (losses) of unconsolidated affiliates	(24.9)	(79.8)	(227.8)	(278.1)
Income tax (benefit) expense	(9.3)	(24.0)	(111.1)	(77.5)
(Loss) earnings before equity in earnings of unconsolidated affiliates	(15.6)	(55.8)	(116.7)	(200.6)
Equity in earnings (losses) of unconsolidated affiliates	0.7	0.5	1.9	3.4
Net (loss) earnings from continuing operations	(14.9)	(55.3)	(114.8)	(197.2)
Assets	9,185.4	9,075.7	9,185.4	9,075.7
Goodwill	2,853.9	2,967.4	2,853.9	2,967.4
Dun & Bradstreet | Restaurant revenue | Operating Segments
Segment Reporting Information [Line Items]
Revenues from external customers	0.0	0.0	0.0	0.0
Dun & Bradstreet | Other operating revenue | Operating Segments
Segment Reporting Information [Line Items]
Revenues from external customers	442.1	408.2	1,258.0	981.2
Optimal Blue | Operating Segments
Segment Reporting Information [Line Items]
Revenues from external customers	6.7		6.7
Interest, investment and other income, including recognized gains and losses, net	0.0		0.0
Total revenues and other income	6.7		6.7
Depreciation and amortization	5.6		5.6
Interest expense	(1.4)		(1.4)
(Loss) earnings before income taxes and equity in earnings (losses) of unconsolidated affiliates	(21.7)		(21.7)
Income tax (benefit) expense	3.4		3.4
(Loss) earnings before equity in earnings of unconsolidated affiliates	(25.1)		(25.1)
Equity in earnings (losses) of unconsolidated affiliates	0.0		0.0
Net (loss) earnings from continuing operations	(25.1)		(25.1)
Assets	2,000.0		2,000.0
Goodwill	1,241.0		1,241.0
Optimal Blue | Restaurant revenue | Operating Segments
Segment Reporting Information [Line Items]
Revenues from external customers	0.0		0.0
Optimal Blue | Other operating revenue | Operating Segments
Segment Reporting Information [Line Items]
Revenues from external customers	6.7		6.7
Corporate and Other
Segment Reporting Information [Line Items]
Goodwill	0.0		0.0			$ 0.0
Corporate and Other | Operating Segments
Segment Reporting Information [Line Items]
Revenues from external customers	10.3	9.3	16.6	19.5
Interest, investment and other income, including recognized gains and losses, net	192.8	93.1	1,688.8	178.7
Total revenues and other income	203.1	102.4	1,705.4	198.2
Depreciation and amortization	0.8	0.5	2.2	1.7
Interest expense	0.1	(3.7)	(0.5)	(10.4)
(Loss) earnings before income taxes and equity in earnings (losses) of unconsolidated affiliates	178.5	80.7	1,623.3	147.8
Income tax (benefit) expense	35.1	15.1	335.6	16.3
(Loss) earnings before equity in earnings of unconsolidated affiliates	143.4	65.6	1,287.7	131.5
Equity in earnings (losses) of unconsolidated affiliates	6.7	0.4	71.8	1.1
Net (loss) earnings from continuing operations	150.1	66.0	1,359.5	132.6
Assets	3,474.5	1,283.6	3,474.5	1,283.6
Goodwill	0.0	0.0	0.0	0.0
Corporate and Other | Restaurant revenue | Operating Segments
Segment Reporting Information [Line Items]
Revenues from external customers	0.0	0.0	0.0	0.0
Corporate and Other | Other operating revenue | Operating Segments
Segment Reporting Information [Line Items]
Revenues from external customers	$ 10.3	$ 9.3	$ 16.6	$ 19.5