Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Accounts and other receivables, allowance for doubtful accounts and sales returns	$ 5,764	$ 3,304
Common stock, no par value
Common stock, shares issued	33,176,024	33,017,422
Common stock, shares outstanding	33,176,024	33,017,422
Common Stock, Shares Held in Employee Trust, Shares	72,510	71,309