CONSOLIDATED BALANCE SHEETS (Unaudited) (Parenthetical) - $ / shares	Sep. 30, 2018	Dec. 31, 2017
Common shareholders' equity:
Common stock, par value (in dollars per share)	$ 0.005	$ 0.005
Common stock, authorized (in shares)	50,000,000	50,000,000
Common stock, issued (in shares)	19,381,762	19,309,829
Common shares outstanding (in shares)	19,381,762	19,309,829