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Significant Accounting Policies - Additional Information (Detail) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2016 USD ($) | Sep. 30, 2016 Segment | Sep. 30, 2015 USD ($)
Accounting Policy [Line Items] |  |  |
Number of operating segment | Segment |  | 1 |
Out-of-Period Adjustment [Member] |  |  |
Accounting Policy [Line Items] |  |  |
Immaterial error correction |  | The out-of-period adjustment is immaterial to the previously filed financial statements and the current period financial statements as presented. The out-of-period adjustment had no impact to the financial statements |
Out-of-Period Adjustment [Member] | Operating Expenses [Member] |  |  |
Accounting Policy [Line Items] |  |  |
Prior period reclassification adjustment | $ (2.2) |  |
Reclassified from Cash and Cash Equivalents to Short-term Investments [Member] |  |  |
Accounting Policy [Line Items] |  |  |
Prior period reclassification adjustment |  |  | $ 8.5
Correction of Overstatement in Investing Activities [Member] |  |  |
Accounting Policy [Line Items] |  |  |
Prior period reclassification adjustment |  |  | $ (8.5)

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- Definition Describes nature and related effect on financial statements related to corrections of prior year errors in the current year financial statements when the effect of the prior year error was immaterial to the prior year financial statements and the current year correction is immaterial to the current year financial statements. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 250 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=64853466&loc=d3e22644-107794 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 250 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SAB Topic 1.N.Q2) -URI http://asc.fasb.org/extlink&oid=26874127&loc=d3e30840-122693 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 250 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB Topic 1.M.1) -URI http://asc.fasb.org/extlink&oid=26874127&loc=d3e30365-122693 + Details
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- Definition Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues. + References No definition available. + Details
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