Income Taxes - Net operating losses (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Operating Loss Carryforwards [Line Items]
Net operating losses	$ 2,900	$ 1,800	$ 1,900
NOLs, annual limitations on use	71
Federal
Operating Loss Carryforwards [Line Items]
Net operating losses	900	800
NOLs, annual limitations on use	33,500
NOLs, without regard to this permanent write-off	33,500
State
Operating Loss Carryforwards [Line Items]
Net operating losses	2,000	1,000
NOLs, annual limitations on use	14,000
NOLs, without regard to this permanent write-off	15,200
Foreign
Operating Loss Carryforwards [Line Items]
Net operating losses	$ 0	$ 0