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Balance Sheet Components - Components of Balance Sheet Accounts (Details) - USD ($) $ in Thousands | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014
--- | --- | --- | --- | ---
Cash and Cash Equivalents [Abstract] |  |  |  |
Cash | $ 61,703 | $ 52,453 |  |
Cash Equivalents, at Carrying Value | 73,608 | 73,468 |  |
Cash and Cash Equivalents, at Carrying Value | 135,311 | 125,921 | $ 104,914 | $ 44,816
Inventory, Finished Goods, Gross | 7,779 | 10,722 |  |
Inventory, Raw Materials and Supplies, Gross | 799 | 617 |  |
Inventory Valuation Reserves | (180) | (82) |  |
Inventories, net | 8,398 | 11,257 |  |
Property and Equipment [Abstract] |  |  |  |
Office equipment | 530 | 517 |  |
Capitalized Computer Software, Gross | 916 | 672 |  |
Machinery and Equipment, Gross | 30 | 28 |  |
Furniture and Fixtures, Gross | 276 | 241 |  |
Leasehold Improvements, Gross | 957 | 840 |  |
Construction in Progress, Gross | 10 | 157 |  |
Property, Plant and Equipment, Gross | 2,719 | 2,455 |  |
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment | 1,570 | 1,067 |  |
Property, Plant and Equipment, Net | 1,149 | 1,388 |  |
Other accrued expenses: |  |  |  |
Accrued Sales Returns | 614 | 1,632 |  |
Accrued Employee Benefits, Current | 5,568 | 10,541 |  |
Accrued Warehousing And Inventory Related Expense | 1,423 | 2,816 |  |
Other Accrued Liabilities, Current | 7,605 | 14,989 |  |
Deferred Revenue [Abstract] |  |  |  |
Deferred Revenue, Current | 4,455 | 4,948 |  |
Unshipped Product [Member] |  |  |  |
Deferred Revenue [Abstract] |  |  |  |
Deferred Revenue | 2,411 | 2,191 |  |
Auto Ship Advances [Member] |  |  |  |
Deferred Revenue [Abstract] |  |  |  |
Deferred Revenue | 1,665 | 2,327 |  |
Enrollment Package Revenue [Member] |  |  |  |
Deferred Revenue [Abstract] |  |  |  |
Deferred Revenue | 379 | $ 430 |  |
China |  |  |  |
Cash and Cash Equivalents [Abstract] |  |  |  |
Cash and Cash Equivalents, at Carrying Value | $ 8,700 |  |  |

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- Definition Carrying value as of the balance sheet date of obligations, excluding pension and other postretirement benefits, incurred through that date and payable for perquisites provided to employees pertaining to services received from them. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.20) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Current Liabilities -URI http://asc.fasb.org/extlink&oid=6509677 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section 45 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=28358313&loc=d3e6935-107765 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section 45 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=28358313&loc=d3e6911-107765 + Details
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- Definition The carrying amount of consideration received or receivable as of the balance sheet date on potential earnings that were not recognized as revenue in conformity with GAAP, and which are expected to be recognized as such within one year or the normal operating cycle, if longer, including sales, license fees, and royalties, but excluding interest income. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 605 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB Topic 13.A.3(b).Q1(c)) -URI http://asc.fasb.org/extlink&oid=65893310&loc=d3e214044-122780 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section 45 -Paragraph 8 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=28358313&loc=d3e6935-107765 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 605 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 13.A.4(a).Q1) -URI http://asc.fasb.org/extlink&oid=65893310&loc=d3e214044-122780 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 605 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB Topic 13.A.3) -URI http://asc.fasb.org/extlink&oid=65893310&loc=d3e214044-122780 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 605 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB Topic 13.A.3(b).Q2) -URI http://asc.fasb.org/extlink&oid=65893310&loc=d3e214044-122780 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 605 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB Topic 13.A.3(b)) -URI http://asc.fasb.org/extlink&oid=65893310&loc=d3e214044-122780 Reference 7: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 605 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB Topic 13.A.3(c).Q3) -URI http://asc.fasb.org/extlink&oid=65893310&loc=d3e214044-122780 + Details
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