Unaudited Quarterly Information - Summary of Quarterly Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 29, 2018	Sep. 29, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 30, 2017	Sep. 30, 2017	Jul. 01, 2017	Apr. 01, 2017	Dec. 29, 2018	Dec. 30, 2017	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 163,935	$ 165,745	$ 154,913	$ 149,193	$ 149,140	$ 152,794	$ 110,242	$ 102,857	$ 633,786	$ 515,033	$ 414,126
Gross Profit	70,945	73,093	68,164	66,079	64,623	64,655	52,852	49,017
Amounts Attributable to Kadant:
Net Income Attributable to Kadant	$ 18,422	$ 18,784	$ 12,349	$ 10,858	$ 760	$ 13,285	$ 8,096	$ 8,951	$ 60,413	$ 31,092	$ 32,077
Basic Earnings per Share:
Net Income Attributable to Kadant (in dollars per share)	$ 1.66	$ 1.69	$ 1.11	$ 0.98	$ 0.07	$ 1.21	$ 0.74	$ 0.82	$ 5.45	$ 2.83	$ 2.95
Earnings Per Share, Diluted [Abstract]
Net Income Attributable to Kadant (in dollars per share)	1.61	1.64	1.08	0.96	0.07	1.17	0.72	0.80	5.30	2.75	2.88
Cash Dividends Declared per Common Share (in dollars per share)	$ 0.22	$ 0.22	$ 0.22	$ 0.22	$ 0.21	$ 0.21	$ 0.21	$ 0.21	$ 0.88	$ 0.84	$ 0.76