Goodwill and intangible assets - Additional Information (Details) - USD ($)	6 Months Ended	12 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Goodwill and intangible assets
Goodwill impairment loss	$ 0		$ 0
Goodwill	47,803,000		$ 47,803,000
Amortization of Intangible Assets	$ 1,432,000	$ 1,474,000

Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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