Accrued expenses and other current liabilities - Summary of restructuring reserve activity (Details) - USD ($)	3 Months Ended	6 Months Ended	13 Months Ended
Jun. 30, 2019	Jun. 30, 2019	Jun. 30, 2019
Restructuring Reserve [Roll Forward]
Accrued restructuring balance as of December 31, 2018		$ 68,593
Adjustments: Employee termination benefits	$ 0	(11,000)	$ 1,765,000
Payments		(57,365)
Accrued restructuring balance as of June 30, 2019	$ 0	0	$ 0
Employee termination benefits
Restructuring Reserve [Roll Forward]
Adjustments: Employee termination benefits		$ (11,228)

Amount of cash payments made as the result of exit or disposal activities. Excludes payments associated with a discontinued operation or an asset retirement obligation.

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- Definition

Amount of expenses associated with exit or disposal activities pursuant to an authorized plan. Excludes expenses related to a discontinued operation or an asset retirement obligation.

+ References

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Carrying amount (including both current and noncurrent portions of the accrual) as of the balance sheet date pertaining to a specified type of cost associated with exit from or disposal of business activities or restructuring pursuant to a duly authorized plan.

+ References

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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