CONSOLIDATED BALANCE SHEETS (UNAUDITED) (Parenthetical)	Jun. 30, 2018 $ / shares shares	Dec. 31, 2017 $ / shares shares
Stockholders' equity
Common stock, par value (in dollars per share) | $ / shares	$ 0	$ 0
Common stock, shares authorized (in shares)	20,000,000	20,000,000
Common stock, shares issued (in shares)	13,362,796	13,345,535
Common stock, shares outstanding (in shares)	13,362,796	13,345,535