Supplemental Financial Data - Other Intangibles (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Feb. 07, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Finite-lived Intangible Assets [Roll Forward]
Additions	$ 0.1	$ 0.6	$ 0.6
Amortization	(3.2)	(456.7)	(425.8)
Other	0.1	7.5	(1.9)
Balance at end of period		3,968.9
Indefinite-lived Intangible Assets [Roll Forward]
Balance at beginning of period	158.4	1,275.8	158.4
Acquisition			1,275.8
Balance at end of period	158.4	1,275.8	1,275.8	$ 158.4
Total
Balance at beginning of period	284.1	5,251.4	284.1
Acquisition		9.2	5,678.5
Additions	0.1	0.6	0.6
Amortization	(3.2)	(456.7)	(425.8)
Other	0.1	7.5	(1.9)
Balance at end of period	281.1	4,812.0	5,251.4	284.1
Customer Relationships
Finite-lived Intangible Assets [Roll Forward]
Balance at beginning of period	75.7	2,162.1	75.7
Additions	0.0	0.0	0.0
Acquisition		2.4	2,403.0
Amortization	(1.7)	(255.1)	(239.5)
Other	0.1	3.1	(1.4)
Balance at end of period	74.1	1,912.5	2,162.1	75.7
Total
Additions	0.0	0.0	0.0
Amortization	(1.7)	(255.1)	(239.5)
Other	0.1	3.1	(1.4)
Accumulated amortization of intangibles	56.6	495.5	239.5
Database and Other
Finite-lived Intangible Assets [Roll Forward]
Balance at beginning of period	50.0	1,813.5	50.0
Additions	0.1	0.6	0.6
Acquisition		6.8	1,999.7
Amortization	(1.5)	(201.6)	(186.3)
Other	0.0	4.4	(0.5)
Balance at end of period	48.6	1,623.7	1,813.5	50.0
Total
Additions	0.1	0.6	0.6
Amortization	(1.5)	(201.6)	(186.3)
Other	0.0	4.4	(0.5)
Accumulated amortization of intangibles	$ 121.4	$ 388.5	$ 186.3
Other Indefinite-Lived Intangibles
Finite-lived Intangible Assets [Roll Forward]
Amortization				(32.9)
Total
Amortization				$ (32.9)