| Summary of Significant Accounting Policies - Leases - Balance Sheet Information (Details) $ in Thousands | Mar. 31, 2019  USD ($) | 
|---|---|
| Summary of Significant Accounting Policies | |
| Operating lease right-of-use assets | $ 24,462 | 
| Financial position | us-gaap:OperatingLeaseRightOfUseAsset | 
| Operating lease liabilities, current | $ (2,217) | 
| Financial position | us-gaap:OperatingLeaseLiabilityCurrent | 
| Operating lease liabilities, non-current | $ (26,779) | 
| Financial position | us-gaap:OperatingLeaseLiabilityNoncurrent | 
| Total operating lease liabilities | $ (4,534) | 
| Financial position | us-gaap:OperatingLeaseLiabilityCurrent us-gaap:OperatingLeaseLiabilityNoncurrent | 
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- Definition Operating lease asset (liability), net No definition available. 
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- References No definition available. 
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- Definition Present value of lessee's discounted obligation for lease payments from operating lease, classified as current. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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- Definition Indicates line item in statement of financial position that includes current operating lease liability. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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- Definition Present value of lessee's discounted obligation for lease payments from operating lease, classified as noncurrent. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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- Definition Indicates line item in statement of financial position that includes noncurrent operating lease liability. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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- Definition Indicates line item in statement of financial position that includes operating lease liability. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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- Definition Amount of lessee's right to use underlying asset under operating lease. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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- Definition Indicates line item in statement of financial position that includes operating lease right-of-use asset. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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