Cash Equivalents and Investments - Restricted Cash and Investments (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 922.5	$ 1,361.9
Total cash, cash equivalents, and restricted cash	942.7	1,383.0	$ 1,276.5	$ 2,505.8
Prepaid expenses and other current assets
Cash and Cash Equivalents [Line Items]
Restricted cash included in Prepaid expenses and other current assets	17.2	19.2
Other long-term assets
Cash and Cash Equivalents [Line Items]
Restricted cash included in Prepaid expenses and other current assets	$ 3.0	$ 1.9