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Schedule II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Schedule II - Valuation and Qualifying Accounts [Roll Forward] |  |  |
Balance at beginning of period | $ 97.9 | $ 86.7 | $ 83.6
Charges to cost and expense | 59.2 | 61.7 | 42.8
Other additions | 0.0 | 0.0 | 0.0
(Deductions) | (51.9) | (50.5) | (39.7)
Balance at end of period | 105.2 | 97.9 | 86.7
Allowance for Credit Losses [Member] |  |  |
Schedule II - Valuation and Qualifying Accounts [Roll Forward] |  |  |
Balance at beginning of period | 10.1 | 16.3 | 8.2
Charges to cost and expense | 12.1 | 1.7 | 8.6
Other additions | 0.0 | 0.0 | 0.0
(Deductions) | (1.7) | (7.9) | (0.5)
Balance at end of period | 20.5 | 10.1 | 16.3
Unbilled Receivable Allowance [Member] |  |  |
Schedule II - Valuation and Qualifying Accounts [Roll Forward] |  |  |
Balance at beginning of period | 31.3 | 22.0 | 27.2
Charges to cost and expense | 38.5 | 49.7 | 33.0
Other additions | 0.0 | 0.0 | 0.0
(Deductions) | (39.4) | (40.4) | (38.2)
Balance at end of period | 30.4 | 31.3 | 22.0
Valuation Allowance for Inventory [Member] |  |  |
Schedule II - Valuation and Qualifying Accounts [Roll Forward] |  |  |
Balance at beginning of period | 7.7 | 7.8 | 7.7
Charges to cost and expense | 1.8 | 2.1 | 1.1
Other additions | 0.0 | 0.0 | 0.0
(Deductions) | (1.0) | (2.2) | (1.0)
Balance at end of period | 8.5 | 7.7 | 7.8
Valuation Allowance for Deferred Tax Assets [Member] |  |  |
Schedule II - Valuation and Qualifying Accounts [Roll Forward] |  |  |
Balance at beginning of period | 48.8 | 40.6 | 40.5
Charges to cost and expense | 6.8 | 8.2 | 0.1
Other additions | 0.0 | 0.0 | 0.0
(Deductions) | (9.8) | 0.0 | 0.0
Balance at end of period | $ 45.8 | $ 48.8 | $ 40.6

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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(Column B)) -URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e24092-122690 Reference 2: 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(Column E)) -URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e24092-122690 + Details
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