Fair Value Measurements, Equity Investments and Other Financial Instruments - Equity Investment Without Readily Determinable Fair Value (Details) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2021 USD ($)	Dec. 31, 2020 USD ($) investment	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)
Equity Securities without Readily Determinable Fair Value [Roll Forward]
Carrying amount at the beginning of period			$ 25.4	$ 7.5	$ 7.5
Purchases			14.7		2.6
Impairments or downward adjustments			0.0		0.0
Upward adjustments			0.0		15.1
Currency translation on investments			(0.3)		0.2
Carrying amount at the end of period	$ 39.8	$ 25.4	39.8		25.4
Cumulative upward adjustment	15.1	$ 15.1	15.1		$ 15.1
Number of investments | investment		1
Additional investment	$ 9.0	$ 5.7	$ 15.0	$ 0.0