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Schedule II - Valuation and Qualifying Accounts (Detail) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Valuation Allowance for Doubtful Accounts [Member] |  |  |
Valuation and Qualifying Accounts Disclosure [Line Items] |  |  |
Balance at Beginning of Year | $ 4,135 | $ 3,909 | $ 1,760
Additions Acquisition Beginning Balance |  |  | 1,292
Additions Charged to Costs and Expenses | 1,435 | 825 | 1,109
Additions Charged to Other Accounts |  |  | (66)
Deductions & Write-offs | (327) | (599) | (186)
Balance at End of Year | 5,243 | 4,135 | 3,909
Valuation Allowance for Sales Returns [Member] |  |  |
Valuation and Qualifying Accounts Disclosure [Line Items] |  |  |
Balance at Beginning of Year | 1,295 | 1,138 | 601
Additions Acquisition Beginning Balance |  |  | 423
Additions Charged to Costs and Expenses | 124 | (142) | 2,262
Deductions & Write-offs | (386) | 299 | (2,148)
Balance at End of Year | 1,033 | 1,295 | 1,138
Valuation Allowance on Deferred Tax Asset [Member] |  |  |
Valuation and Qualifying Accounts Disclosure [Line Items] |  |  |
Balance at Beginning of Year | 13,629 | 12,527 | 6,127
Additions Acquisition Beginning Balance |  |  | 3,769
Additions Charged to Costs and Expenses | 4,825 | 1,603 | 2,719
Deductions & Write-offs | (518) | (501) | (88)
Balance at End of Year | $ 17,936 | $ 13,629 | $ 12,527

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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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