The Company and Summary of Significant Accounting Principles - Schedule of Concentrations Equal to or Exceeding 10% of Company's Accounts Receivable, Revenue, and Cost of Revenue (Detail) - Customer Concentration Risk [Member]
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3 Months Ended |
9 Months Ended |
12 Months Ended |
Sep. 30, 2017 |
Sep. 30, 2016 |
Sep. 30, 2017 |
Sep. 30, 2016 |
Dec. 31, 2016 |
| Accounts Receivable [Member] |
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| Concentration Risk [Line Items] |
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| Concentration risk, percentage |
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10.00%
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10.00%
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| Accounts Receivable [Member] | Google Search [Member] |
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| Concentration Risk [Line Items] |
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| Concentration risk, percentage |
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9.00%
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| Accounts Receivable [Member] | Advertising Customer [Member] |
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| Concentration Risk [Line Items] |
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| Concentration risk, percentage |
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14.00%
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| Accounts Receivable [Member] | Google Advertising Affiliate [Member] |
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| Concentration Risk [Line Items] |
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| Concentration risk, percentage |
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17.00%
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| Revenue [Member] |
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| Concentration Risk [Line Items] |
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| Concentration risk, percentage |
10.00%
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10.00%
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10.00%
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10.00%
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| Revenue [Member] | Google Search [Member] |
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| Concentration Risk [Line Items] |
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| Concentration risk, percentage |
17.00%
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10.00%
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15.00%
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14.00%
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| Revenue [Member] | Google Advertising Affiliate [Member] |
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| Concentration Risk [Line Items] |
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| Concentration risk, percentage |
22.00%
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19.00%
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| Cost of Revenue [Member] | Customer A [Member] |
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| Concentration Risk [Line Items] |
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| Concentration risk, percentage |
11.00%
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22.00%
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13.00%
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26.00%
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| Cost of Revenue [Member] | Customer B [Member] |
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| Concentration Risk [Line Items] |
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| Concentration risk, percentage |
27.00%
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16.00%
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| Cost of Revenue [Member] | Customer C [Member] |
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| Concentration Risk [Line Items] |
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| Concentration risk, percentage |
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10.00%
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