Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Accounts and other receivables, allowance for doubtful accounts and sales returns	$ 2,937	$ 3,304
Common stock, no par value (shares)
Common stock, shares authorized (shares)	150,000,000	150,000,000
Common stock, shares, issued (shares)	33,176,024	33,017,422
Common stock, shares, outstanding (shares)	33,176,024	33,017,422
Common stock held in trust for savings restoration plan (shares)	72,883	71,309