Amount of cash and cash equivalents restricted as to withdrawal or usage. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits. Cash equivalents include, but are not limited to, short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Name:	us-gaap_RestrictedCashAndCashEquivalents
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Cash, Cash Equivalents, and Restricted Cash (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 775.6	$ 452.3
Restricted cash	43.1	40.1
Total cash, cash equivalents, and restricted cash	818.7	492.4	$ 42.0
Cash
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	219.2	56.7
Money market funds
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	556.4	372.1
Treasury bills
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	0.0	23.5
Fiduciary assets
Cash and Cash Equivalents [Line Items]
Restricted cash	25.0	12.1
Letters of credit and cash on deposit
Cash and Cash Equivalents [Line Items]
Restricted cash	$ 18.1	$ 28.0