Operating Segment and Related Information - Long-term investments, Property and Equipment and Assets (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Revenues from External Customers and Long-Lived Assets [Line Items]
Investments	$ 49.9	$ 55.4
Total Assets	1,221.5	6,742.8
Operating Segments | Infrastructure
Revenues from External Customers and Long-Lived Assets [Line Items]
Investments	0.9	0.9
Total Assets	917.7	494.8
Operating Segments | Life Sciences
Revenues from External Customers and Long-Lived Assets [Line Items]
Investments	13.0	18.4
Total Assets	29.3	21.4
Operating Segments | Spectrum
Revenues from External Customers and Long-Lived Assets [Line Items]
Total Assets	199.8	213.6
Operating Segments | Other
Revenues from External Customers and Long-Lived Assets [Line Items]
Investments	36.0	36.1
Total Assets	38.9	6,021.3
Non-operating Corporate
Revenues from External Customers and Long-Lived Assets [Line Items]
Total Assets	35.8	30.1
Eliminations
Revenues from External Customers and Long-Lived Assets [Line Items]
Total Assets	$ 0.0	$ (38.4)