Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Statement Of Financial Position [Abstract]
Trade accounts receivable, allowance for doubtful accounts	$ 8,923	$ 7,285
Common shares, par value	$ 0.10	$ 0.10
Common shares, authorized	50,000,000	50,000,000
Common shares, issued	18,659,696	18,611,495
Common shares, outstanding	18,659,696	18,611,495