CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
CONSOLIDATED BALANCE SHEETS
Valuation allowance	$ 61,408	$ 50,652
Common stock, shares authorized (in shares)	90,000,000	90,000,000
Common stock, no par value (in dollars per share)	$ 0	$ 0
Common stock, shares issued (in shares)	25,713,408	25,623,016
Common stock, shares outstanding (in shares)	25,239,748	25,444,275
Treasury stock, at cost	473,660	178,741