Fair value measurements (Tables)

6 Months Ended

12 Months Ended

Jun. 30, 2019

Dec. 31, 2018

Fair Value Disclosures [Abstract]

Schedule of Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis

The following table sets forth a summary of changes in the fair value of level 3 liabilities measured at fair value on a recurring basis for the six months ended June 30, 2019:

Description	Balance at December 31, 2018		Change in Fair Value			Balance at June 30, 2019
Warrant liability	$	67	$	(67	)	$	—

The following table sets forth a summary of changes in the fair value of level 3 liabilities measured at fair value on a recurring basis for the year ended December 31, 2018:  

Description	Balance at December 31, 2017		Change in Fair Value			Balance at December31, 2018
Warrant liability	$	8,453	$	(8,386	)	$	67