Schedule II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Valuation and qualifying accounts
Balance at beginning of period	$ 143.2	$ 108.0	$ 113.3
Expense	94.7	96.7	87.4
Deferral	(5.5)	16.4	(5.9)
Net write-offs	(83.2)	(77.9)	(86.8)
Balance at end of period	$ 149.2	$ 143.2	$ 108.0

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

No definition available.

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- Definition

Amount of valuation and qualifying accounts and reserves.

+ References

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

+ Details

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- Definition

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

+ References

+ Details

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- Definition

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

+ References

+ Details

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- Definition

Amount of decrease in valuation and qualifying accounts and reserves.

+ References

+ Details

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