Investments - Schedule of Summarized Financial Information, D&B and AmeriLife (Details) - USD ($) $ in Millions		3 Months Ended		5 Months Ended	6 Months Ended
	Mar. 31, 2020	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Condensed Combined Balance Sheets
Total current assets		$ 1,083.4			$ 1,083.4		$ 630.9
Total assets		3,788.6	$ 1,852.2	$ 1,852.2	3,788.6	$ 1,852.2	2,092.2
Current liabilities		188.8			188.8		198.7
Long-term debt		70.4			70.4		127.1
Total liabilities		654.8			654.8		562.4
Total capital	$ 2,205.0	3,133.8	1,232.2	1,232.2	3,133.8	1,232.2	1,529.8	$ 1,202.5	$ 1,199.7
Total liabilities and equity		3,788.6			3,788.6		2,092.2
Equity Method Investment, Financial Statement, Reported Amounts [Abstract]
Total revenues		689.0	348.7		1,779.3	623.6
Operating loss		(45.7)	(21.4)		(99.0)	(32.5)
Net loss		466.1	18.9		1,104.2	(1.0)
Income attributable to noncontrolling interests		(9.2)	(4.5)		(18.8)	$ (7.6)
Unconsolidated affiliates | Dun And Bradstreet Corporation
Condensed Combined Balance Sheets
Total current assets		489.0			489.0		417.9
Goodwill and other intangible assets, net		7,870.3			7,870.3		8,091.5
Other assets		625.8			625.8		603.4
Total assets							9,112.8
Current liabilities		2,453.6			2,453.6		1,090.4
Long-term debt		3,620.7			3,620.7		3,818.9
Other non-current liabilities		1,521.8			1,521.8		1,594.0
Total liabilities		7,596.1			7,596.1		6,503.3
Preferred equity		0.0			0.0		1,030.6
Total capital		1,389.0			1,389.0		1,578.9
Total liabilities and equity		8,985.1			8,985.1		$ 9,112.8
Equity Method Investment, Financial Statement, Reported Amounts [Abstract]
Total revenues		420.6	398.9	573.0	815.9
Loss before income taxes		(201.9)	(86.4)	(198.3)	(202.9)
Net loss		(173.8)	(60.5)	(141.9)	(99.9)
Dividends attributable to preferred equity and noncontrolling interest expense		(33.3)	(33.5)	(51.8)	(65.7)
Net income (loss)		$ (207.1)	$ (94.0)	$ (193.7)	$ (165.6)
Unconsolidated affiliates | AmeriLife
Condensed Combined Balance Sheets
Total current assets	152.3
Goodwill and other intangible assets, net	1,075.5
Other assets	15.0
Total assets	1,242.8
Current liabilities	40.8
Long-term debt	538.3
Other non-current liabilities	6.2
Total liabilities	585.3
Member's equity	597.6
Noncontrolling interest - nonredeemable	59.9
Total member's equity	657.5
Total liabilities and equity	1,242.8
Equity Method Investment, Financial Statement, Reported Amounts [Abstract]
Total revenues	14.7
Operating loss	(16.1)
Net loss	(16.9)
Income attributable to noncontrolling interests	0.4
Net income (loss)	$ (17.3)