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Basis of Presentation and Significant Accounting Policies - Additional Information (Details) | 3 Months Ended | 6 Months Ended | 12 Months Ended
--- | --- | --- | ---
Jun. 30, 2018 USD ($) Customer | Jun. 30, 2017 USD ($) Customer | Jun. 30, 2018 USD ($) Customer | Jun. 30, 2017 USD ($) Customer | Dec. 31, 2017 USD ($) Customer
Basis Of Presentation And Significant Accounting Policies [Line Items] |  |  |  |  |  |
Allocation of undistributed earnings to participating securities |  | $ 113,000 | $ 0 | $ 0 |  |
Contractual obligation | $ 0 | $ 0 | 0 | $ 0 |  |
Cash equivalents | 38,690,000 |  | 38,690,000 |  | $ 43,471,000 | [1]
Customer Concentration Risk [Member] |  |  |  |  |  |
Basis Of Presentation And Significant Accounting Policies [Line Items] |  |  |  |  |  |
Cash equivalents | $ 0 |  | $ 0 |  |  |
Customer Concentration Risk [Member] | Trade Receivables [Member] |  |  |  |  |  |
Basis Of Presentation And Significant Accounting Policies [Line Items] |  |  |  |  |  |
Number of major partners | Customer |  |  | 2 |  | 1 |
Customer Concentration Risk [Member] | Trade Receivables [Member] | Partner 1 [Member] |  |  |  |  |  |
Basis Of Presentation And Significant Accounting Policies [Line Items] |  |  |  |  |  |
Concentration risk, percentage (in hundredths) |  |  | 84.00% |  | 95.00% |
Customer Concentration Risk [Member] | Trade Receivables [Member] | Partner 2 [Member] |  |  |  |  |  |
Basis Of Presentation And Significant Accounting Policies [Line Items] |  |  |  |  |  |
Concentration risk, percentage (in hundredths) |  |  | 16.00% |  |  |
Customer Concentration Risk [Member] | Revenues [Member] |  |  |  |  |  |
Basis Of Presentation And Significant Accounting Policies [Line Items] |  |  |  |  |  |
Number of major partners | Customer | 2 | 1 | 2 | 1 |  |
Customer Concentration Risk [Member] | Revenues [Member] | Partner 1 [Member] |  |  |  |  |  |
Basis Of Presentation And Significant Accounting Policies [Line Items] |  |  |  |  |  |
Concentration risk, percentage (in hundredths) | 80.00% | 92.00% | 66.00% | 90.00% |  |
Customer Concentration Risk [Member] | Revenues [Member] | Partner 2 [Member] |  |  |  |  |  |
Basis Of Presentation And Significant Accounting Policies [Line Items] |  |  |  |  |  |
Concentration risk, percentage (in hundredths) | 11.00% |  | 22.00% |  |  |
[1] | The condensed consolidated balance sheet as of December 31, 2017 has been derived from the audited consolidated financial statements as of that date included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2017.

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- Definition Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3044-108585 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section 45 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=82887183&loc=d3e6676-107765 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.1) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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