Acquisitions - Additional Information (Details) $ / shares in Units, € in Thousands, $ in Thousands							3 Months Ended									12 Months Ended
	Apr. 04, 2016 USD ($)	Apr. 04, 2016 EUR (€)	Jan. 04, 2016 USD ($)	Jan. 04, 2016 EUR (€)	Oct. 31, 2014 USD ($)	Dec. 30, 2013 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($) $ / shares	Oct. 01, 2016 $ / shares	Jul. 02, 2016 $ / shares	Apr. 02, 2016 USD ($) $ / shares	Jan. 02, 2016 USD ($) $ / shares	Oct. 03, 2015 $ / shares	Jul. 04, 2015 $ / shares	Apr. 04, 2015 $ / shares	Dec. 31, 2016 USD ($) $ / shares	Jan. 02, 2016 USD ($) $ / shares	Jan. 03, 2015 USD ($) $ / shares
Business Acquisition [Line Items]
Acquisition transaction costs																$ 1,832		$ 326
Acquisitions, net of cash acquired																$ 56,617	$ 0	$ 11,984
Net Loss Attributable to Kadant (in dollars per share) | $ / shares								$ (0.69)	$ (0.82)	$ (0.75)	$ (0.62)	$ (0.94)	$ (0.78)	$ (0.76)	$ (0.62)	$ (2.88)	$ (3.10)	$ (2.56)
Goodwill								$ 151,455				$ 119,051				$ 151,455	$ 119,051	$ 127,882
Weighted average useful life of acquired intangible assets																12 years
Cash payments in acquisition																$ 58,894	$ 0	12,658
Euro-Denominated Borrowing | Revolving credit facility
Business Acquisition [Line Items]
Proceeds from revolving credit facility											$ 29,866
PAAL
Business Acquisition [Line Items]
Acquisitions, net of cash acquired	$ 56,617	€ 49,713
Revenues																$ 40,783
Net Loss Attributable to Kadant (in dollars per share) | $ / shares																$ 0.01
Acquisition costs per share (in dollars per share) | $ / shares																0.15
One-time charges associated with acquired inventory and backlog per share (in dollars per share) | $ / shares																$ 0.12
Goodwill	38,552
Weighted average useful life of acquired intangible assets																12 years
PAAL | Customer relationships
Business Acquisition [Line Items]
Intangible assets	15,831
Weighted average useful life of acquired intangible assets																13 years
PAAL | Intellectual property
Business Acquisition [Line Items]
Intangible assets	4,203
Weighted average useful life of acquired intangible assets																9 years
PAAL | Tradenames
Business Acquisition [Line Items]
Intangible assets	2,278
Weighted average useful life of acquired intangible assets																14 years
PAAL | Other intangibles
Business Acquisition [Line Items]
Intangible assets	$ 2,379
Certain assets of the screen cylinder business of a U.S.-based company
Business Acquisition [Line Items]
Cash payments in acquisition					$ 9,174
European Producer of Creping and Coating Blades
Business Acquisition [Line Items]
Cash payments in acquisition			$ 1,091	€ 1,000		$ 2,666
Cash acquired from acquisition						$ 674
2014 Acquisitions
Business Acquisition [Line Items]
Goodwill																		3,463
Weighted average useful life of acquired intangible assets																9 years
Cash payments in acquisition																		11,840
Goodwill, expected tax deductible amount																		2,004
2014 Acquisitions | Customer relationships
Business Acquisition [Line Items]
Weighted average useful life of acquired intangible assets																8 years
2014 Acquisitions | Intellectual property
Business Acquisition [Line Items]
Weighted average useful life of acquired intangible assets																11 years
2013 Acquisitions
Business Acquisition [Line Items]
Post-closing adjustment payments, for prior acquisitions																		$ 818
Scenario, Forecast | PAAL
Business Acquisition [Line Items]
Cash payments in acquisition							$ 165