Income Taxes - Valuation allowance (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Net deferred tax assets and (liabilities)
Gross deferred tax assets	$ 32,622	$ 58,464
Net deferred tax liability	16	5,643
Valuation allowance	32,606	52,821
NOL expiring	43,106
NOL carried forward indefinitely	10,952
Federal
Net deferred tax assets and (liabilities)
Credits or net operating losses	$ 54,058	$ 71,449