Subsequent Event - Pro Forma Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	6 Months Ended
Jul. 03, 2021	Jun. 27, 2020	Jul. 03, 2021	Jun. 27, 2020
Pro Forma Information
Cost of revenue	$ 110,493	$ 86,412	$ 207,241	$ 177,216
Selling, general, and administrative expenses	49,267	45,073	98,698	90,665
The Clouth Group of Companies
Subsequent Event [Line Items]
Revenues	207,740	164,248	392,128	334,796
Net Income Attributable to Kadant	$ 23,663	$ 10,276	$ 41,522	$ 20,147
Earnings per Share Attributable to Kadant:
Basic (in dollars per share)	$ 2.04	$ 0.89	$ 3.59	$ 1.76
Diluted (in dollars per share)	$ 2.03	$ 0.89	$ 3.57	$ 1.75
The Clouth Group of Companies \| Fair Value Adjustment to Inventory
Pro Forma Information
Cost of revenue		$ 1,753		$ 3,505
The Clouth Group of Companies \| Acquisition-related Costs
Pro Forma Information
Selling, general, and administrative expenses		$ 239		$ 1,673
Amortization	$ 239		$ 1,236

Business Acquisition, Pro Forma Earnings Per Share [Abstract]

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The aggregate amount of recurring noncash expense charged against earnings in the period to allocate the cost of assets over their estimated remaining economic lives.

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The pro forma basic net income per share for a period as if the business combination or combinations had been completed at the beginning of a period.

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The pro forma diluted net income per share for a period as if the business combination or combinations had been completed at the beginning of a period.

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The pro forma net Income or Loss for the period as if the business combination or combinations had been completed at the beginning of a period.

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The pro forma revenue for a period as if the business combination or combinations had been completed at the beginning of the period.

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The aggregate costs related to goods produced and sold and services rendered by an entity during the reporting period. This excludes costs incurred during the reporting period related to financial services rendered and other revenue generating activities.

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The aggregate total costs related to selling a firm's product and services, as well as all other general and administrative expenses. Direct selling expenses (for example, credit, warranty, and advertising) are expenses that can be directly linked to the sale of specific products. Indirect selling expenses are expenses that cannot be directly linked to the sale of specific products, for example telephone expenses, Internet, and postal charges. General and administrative expenses include salaries of non-sales personnel, rent, utilities, communication, etc.

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Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.

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