Summary of Significant Accounting Policies - Schedule of Earnings Per Share, Basic and Diluted (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions		1 Months Ended	12 Months Ended
	Jun. 01, 2023	Jun. 30, 2023	Dec. 28, 2024	Dec. 30, 2023	Dec. 31, 2022
Numerator:
Numerator for both basic and diluted EPS attributable to HNI Corporation net income			$ 139.5	$ 49.2	$ 123.9
Denominators:
Denominator for basic EPS weighted-average common shares outstanding (in shares)			47.4	44.5	41.7
Potentially dilutive shares from stock-based compensation plans (in shares)			1.1	0.8	0.5
Denominator for diluted EPS (in shares)			48.5	45.4	42.2
Earnings per share - basic (in dollars per share)			$ 2.95	$ 1.11	$ 2.97
Earnings per share - diluted (in dollars per share)			$ 2.88	$ 1.09	$ 2.94
Stock Compensation Plan
Denominators:
Common stock equivalents excluded because their inclusion would be anti-dilutive (in shares)			0.4	2.1	2.0
Kimball International, Inc | Common Stock
Denominators:
Number of shares exchanged (in shares)	4.7	4.7