Investments - Schedule of Summarized Financial Information, Dun & Bradstreet (Details) - USD ($) $ in Millions	3 Months Ended		5 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Jun. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 15, 2020	Jun. 30, 2020	Dec. 31, 2019	Dec. 31, 2018
Condensed Combined Balance Sheets
Total current assets	$ 493.1			$ 493.1				$ 630.9
Total assets	3,868.6	$ 1,893.7		3,868.6	$ 1,893.7	$ 2,000.0		2,092.2
Current liabilities	159.0			159.0				198.7
Long-term debt	70.3			70.3				127.1
Total liabilities	596.6			596.6				562.4
Total equity	3,272.0	1,274.7	$ 1,232.2	3,272.0	1,274.7		$ 3,133.8	1,529.8	$ 1,199.7
Total liabilities and equity	3,868.6			3,868.6				2,092.2
Equity Method Investment, Financial Statement, Reported Amounts [Abstract]
Total revenues	334.0	351.2		2,113.3	974.8
Net loss	128.0	41.6		1,232.2	40.6
Operating Segments | Dun And Bradstreet Corporation
Condensed Combined Balance Sheets
Total assets	9,185.4	9,075.7		9,185.4	9,075.7
Equity Method Investment, Financial Statement, Reported Amounts [Abstract]
Total revenues	432.8	415.0		1,216.5	$ 1,001.9
Dun And Bradstreet Corporation | Unconsolidated affiliates
Condensed Combined Balance Sheets
Total current assets	723.4			723.4				417.9
Goodwill and other intangible assets, net	7,779.2			7,779.2				8,091.5
Other assets	682.8			682.8				603.4
Total assets								9,112.8
Current liabilities	785.7			785.7				1,090.4
Long-term debt	3,257.5			3,257.5				3,818.9
Other non-current liabilities	1,478.5			1,478.5				1,594.0
Total liabilities	5,521.7			5,521.7				6,503.3
Preferred equity	0.0			0.0				1,030.6
Total equity	3,663.7			3,663.7				1,578.9
Total liabilities and equity	9,185.4			9,185.4				$ 9,112.8
Equity Method Investment, Financial Statement, Reported Amounts [Abstract]
Total revenues	442.1	408.2	981.2	1,258.0
Loss before income taxes	(24.9)	(79.8)	(278.1)	(227.8)
Net loss	(14.9)	(55.3)	(197.2)	(114.8)
Dividends attributable to preferred equity and noncontrolling interest expense	(2.1)	(33.5)	(85.3)	(67.8)
Net loss	$ (17.0)	$ (88.8)	$ (282.5)	$ (182.6)