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Commitments and contingencies (Detail) | 12 Months Ended
--- | ---
Dec. 31, 2017 USD ($)
Auburn, Washington |
Rent Expense [Line Items] |
Rent expense | $ 39,000
Lease Expiration Date | Aug. 31, 2018
Baton Rouge, Louisiana |
Rent Expense [Line Items] |
Rent expense | $ 23,000
Lease Expiration Date | May 31, 2019
Champaign, Illinois |
Rent Expense [Line Items] |
Rent expense | $ 504,000
Lease Expiration Date | Dec. 31, 2018
Charlotte, North Carolina |
Rent Expense [Line Items] |
Rent expense | $ 26,000
Lease Expiration Date | May 31, 2019
Escondido, California |
Rent Expense [Line Items] |
Rent expense | $ 36,000
Lease Expiration Period Description | Month to Month
Hampstead, New Hampshire |
Rent Expense [Line Items] |
Rent expense | $ 52,000
Lease Expiration Date | Aug. 31, 2022
Nashville, Tennessee |
Rent Expense [Line Items] |
Rent expense | $ 173,000
Lease Expiration Date | Mar. 31, 2018
Ontario, California |
Rent Expense [Line Items] |
Rent expense | $ 90,000
Lease Expiration Date | Dec. 31, 2018
Pearl River, New York |
Rent Expense [Line Items] |
Rent expense | $ 150,000
Lease Expiration Date | Dec. 31, 2021
Pottsboro, Texas |
Rent Expense [Line Items] |
Rent expense | $ 6,000
Lease Expiration Date | Aug. 31, 2017
Catano, Puerto Rico |
Rent Expense [Line Items] |
Rent expense | $ 124,000
Lease Expiration Date | Dec. 31, 2020
Stony Point, New York |
Rent Expense [Line Items] |
Rent expense | $ 90,000
Lease Expiration Date | Jun. 30, 2021
Tulsa, Oklahoma |
Rent Expense [Line Items] |
Rent expense | $ 27,000
Lease Expiration Date | Dec. 31, 2017
Long Beach, California [Member] |
Rent Expense [Line Items] |
Rent expense | $ 26,400
Lease Expiration Date | Feb. 29, 2020
Long Island City, New York [Member] |
Rent Expense [Line Items] |
Rent expense | $ 782,000
Lease Expiration Date | Jul. 31, 2018
Riverside, California [Member] |
Rent Expense [Line Items] |
Rent expense | $ 27,000
Lease Expiration Period Description | Month to Month
Smyrna, Georgia [Member] |
Rent Expense [Line Items] |
Rent expense | $ 446,000
Lease Expiration Date | Jul. 31, 2030

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