CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
CONSOLIDATED BALANCE SHEETS
Valuation allowance	$ 50,652	$ 48,453
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)	25,623,016	25,301,732
Common stock, shares outstanding (in shares)	25,444,275	25,128,773
Treasury stock, at cost	178,741	172,959