BASIS OF PRESENTATION - Other Expense (Income) (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
BASIS OF PRESENTATION
Derivative liability fair value adjustment for embedded conversion feature in the Convertible Notes		$ (0.5)
Derivative asset fair value adjustment for contingent call option related to the Class B common stock purchase and cancellation agreement		20.1
Credit losses (gain) related to contingent lease guarantees	$ (2.0)	5.3
Governmental assistance due to COVID-19	(12.4)
Foreign currency transaction (gains) losses	(3.8)	2.0
Non-operating components of net periodic benefit cost	(0.2)
Financing fees related to modification of debt	1.0
Total other expense (income)	$ (17.4)	$ 26.9

The fair value adjustment of a derivative asset.

No definition available.

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- Definition

The fair value adjustment of a derivative liability.

+ References

No definition available.

+ Details

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- Definition

The amount of estimated credit income losses relating to contingent lease guarantees.

+ References

No definition available.

+ Details

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- Definition

The amount of governmental assistance due to COVID-19.

+ References

No definition available.

+ Details

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- Definition

Net Periodic Benefit Cost (Credit), Total

+ References

No definition available.

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- Definition

Amount before tax of foreign currency transaction realized gain (loss) recognized in the income statement.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 830
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6450222&loc=d3e30840-110895

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 830
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=109240200&loc=d3e30690-110894

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- Definition

For a debtor, the aggregate gain (loss) recognized on the restructuring of payables arises from the difference between the book value of the debt before the restructuring and the fair value of the payments on the debt after restructuring is complete.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 60
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6402221&loc=d3e15743-112638

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- References

No definition available.

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- Definition

Amount of income (expense) related to nonoperating activities, classified as other.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.9)
-URI http://asc.fasb.org/extlink&oid=120395209&loc=SL114868664-224227

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