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Basis of Presentation and Significant Accounting Policies - Additional Information (Details) | 3 Months Ended | 12 Months Ended |
--- | --- | --- | ---
Mar. 31, 2019 USD ($) Customer | Mar. 31, 2018 USD ($) Customer | Dec. 31, 2018 USD ($) Customer | Jan. 01, 2019 USD ($)
Basis Of Presentation And Significant Accounting Policies [Line Items] |  |  |  |
Operating lease right-of-use assets | $ 6,906,000 |  |  |
Operating lease liabilities | 8,648,000 |  |  |
Dividends declared | 0 | $ 0 |  |
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 | 1 |  | 2 |
Customer Concentration Risk [Member] | Trade Receivables [Member] | Partner 1 [Member] |  |  |  |
Basis Of Presentation And Significant Accounting Policies [Line Items] |  |  |  |
Concentration risk, percentage (in hundredths) |  |  | 67.00% |
Customer Concentration Risk [Member] | Trade Receivables [Member] | Partner 2 [Member] |  |  |  |
Basis Of Presentation And Significant Accounting Policies [Line Items] |  |  |  |
Concentration risk, percentage (in hundredths) |  |  | 28.00% |
Customer Concentration Risk [Member] | Revenues [Member] |  |  |  |
Basis Of Presentation And Significant Accounting Policies [Line Items] |  |  |  |
Number of major partners | Customer | 1 | 2 |  |
Customer Concentration Risk [Member] | Revenues [Member] | Partner 1 [Member] |  |  |  |
Basis Of Presentation And Significant Accounting Policies [Line Items] |  |  |  |
Concentration risk, percentage (in hundredths) | 99.00% | 86.00% |  |
Customer Concentration Risk [Member] | Revenues [Member] | Partner 2 [Member] |  |  |  |
Basis Of Presentation And Significant Accounting Policies [Line Items] |  |  |  |
Concentration risk, percentage (in hundredths) |  | 13.00% |  |
ASC 842 [Member] |  |  |  |
Basis Of Presentation And Significant Accounting Policies [Line Items] |  |  |  |
Operating lease right-of-use assets |  |  |  | $ 7,400,000
Operating lease liabilities |  |  |  | $ 9,200,000
ASC 842 [Member] | Lease-related Costs [Member] |  |  |  |
Basis Of Presentation And Significant Accounting Policies [Line Items] |  |  |  |
Lease-related restructuring liabilities, carrying amount |  |  | $ 1,700,000 |

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