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SCHEDULE II VALUATION AND QUALIFYING ACCOUNTS (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Allowance for Doubtful Accounts |  |  |
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward] |  |  |
Balance Beginning of Period | $ 16,173 | $ 15,046 | $ 15,194
Additions Charged to Operating Expense | 15,817 | 7,901 | 6,907
Deductions from Reserves | 5,622 | 6,774 | 7,055
Balance End of Period | 26,368 | 16,173 | 15,046
Revenue Allowance |  |  |
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward] |  |  |
Balance Beginning of Period | 11,626 | 14,203 | 16,232
Additions Charged to Operating Expense | 41,338 | 24,862 | 24,252
Deductions from Reserves | 35,017 | 27,439 | 26,281
Balance End of Period | 17,947 | 11,626 | 14,203
Valuation Allowance on Deferred Tax Assets |  |  |
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward] |  |  |
Balance Beginning of Period | 68,355 | 55,189 | 30,916
Additions Charged to Operating Expense | 10,466 | 9,052 | 22,564
Deductions from Reserves | 474 | 4,114 | 1,709
Balance End of Period | $ 79,295 | $ 68,355 | $ 55,189

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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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