CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2017	Dec. 31, 2016
Stockholders' equity
Common stock, par value (in dollars per share)	$ 0	$ 0
Common stock, shares authorized (in shares)	20,000,000	20,000,000
Common stock, shares issued (in shares)	10,676,428	10,640,735
Common stock, shares outstanding (in shares)	10,676,428	10,640,735