Stock repurchases (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Jul. 31, 2019
Stock repurchases
Number of shares repurchased under the stock repurchase program	0	56,000
Cost of shares repurchased under the stock repurchase program		$ 745,000
Weighted average price of shares repurchased (in USD per share)		$ 13.24
Maximum
Stock repurchases
Amount of common stock approved by the entity for a stock repurchase program			$ 20,000,000