Schedule II - Valuation and Qualifying Accounts - Allowance for Doubtful Accounts and Revenue Adjustments (Details) - SEC Schedule, 12-09, Allowance, Credit Loss [Member] - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Balance at beginning of year	$ 35.8	$ 24.0	$ 13.4
Charged to expense/against revenue	34.2	35.7	29.3
Write-offs, net of recoveries	(47.5)	(23.9)	(18.7)
Balance at end of year	$ 22.5	$ 35.8	$ 24.0

Amount of valuation and qualifying accounts and reserves.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 4
-Subparagraph (SX 210.12-09)
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24092-122690

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Amount of increase in valuation and qualifying accounts and reserves from charge to cost and expense.

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Amount of decrease in valuation and qualifying accounts and reserves.

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