Earnings per Share - Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Oct. 01, 2016	Sep. 30, 2017	Oct. 01, 2016
Amounts Attributable to Kadant:
Income from Continuing Operations	$ 13,285	$ 9,154	$ 30,332	$ 24,341
Income from Discontinued Operation	0	3	0	3
Net Income	$ 13,285	$ 9,157	$ 30,332	$ 24,344
Basic Weighted Average Shares (in shares)	11,004	10,901	10,986	10,854
Effect of Stock Options, Restricted Stock Units and Employee Stock Purchase Plan Shares (in shares)	340	288	296	266
Diluted Weighted Average Shares (in shares)	11,344	11,189	11,282	11,120
Basic Earnings per Share (in dollars per share)	$ 1.21	$ 0.84	$ 2.76	$ 2.24
Diluted Earnings per Share (in dollars per share)	$ 1.17	$ 0.82	$ 2.69	$ 2.19