Fair Value Measurements - Summary of Financial Instruments Measured at Fair Value on Recurring Basis (Parenthetical) (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Cash and Cash Equivalents and Short-Term Investments
Financial Instruments Measured at Fair Value on a Recurring Basis [Line Items]
Cash	$ 339.2	$ 248.0
Cash and Cash Equivalents and Short-Term Investments \| Fair Value Measurements on a Recurring Basis
Financial Instruments Measured at Fair Value on a Recurring Basis [Line Items]
Cash	339.2	248.0
Term Deposits	105.0
Restricted Cash and Cash Equivalents and Restricted Investments
Financial Instruments Measured at Fair Value on a Recurring Basis [Line Items]
Restricted cash	57.6	50.2
Restricted Cash and Cash Equivalents and Restricted Investments \| Fair Value Measurements on a Recurring Basis
Financial Instruments Measured at Fair Value on a Recurring Basis [Line Items]
Restricted cash	57.6	50.2
Prepaid Expenses and Other Current Assets
Financial Instruments Measured at Fair Value on a Recurring Basis [Line Items]
Restricted cash	2.1	1.4
Prepaid Expenses and Other Current Assets \| Fair Value Measurements on a Recurring Basis
Financial Instruments Measured at Fair Value on a Recurring Basis [Line Items]
Restricted cash	$ 2.1	$ 1.4

Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Excludes cash and cash equivalents within disposal group and discontinued operation.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.1)
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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

For banks and other depository institutions (including Federal Reserve Banks, if applicable): Interest-bearing deposits in other financial institutions for relatively short periods of time including, for example, certificates of deposits, which are presented separately from cash on the balance sheet.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
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- Definition

Amount of cash restricted as to withdrawal or usage, classified as noncurrent. 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.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
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-SubTopic 10
-Section 45
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Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
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-Section S99
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-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
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-Section 50
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-URI http://asc.fasb.org/extlink&oid=98513485&loc=SL98516268-108586

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-Publisher FASB
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