CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Valuation allowance	$ 44,563	$ 43,718
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)	25,185,619	25,096,087
Common stock, shares outstanding (in shares)	25,021,759	24,937,865
Treasury stock, at cost	163,860	158,222