SEGMENT REPORTING - Net Sales by Business Unit (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 27, 2026	Jun. 28, 2025	Jun. 27, 2026	Jun. 28, 2025
Revenue
Total Net Sales	$ 1,882,937	$ 1,835,374	$ 3,344,204	$ 3,430,893
Corporate
Revenue
Total Net Sales	2,245	1,865	4,225	3,755
Retail \| UFP Edge
Revenue
Total Net Sales	27,015	33,132	48,773	60,625
Retail \| Operating Segments
Revenue
Total Net Sales	818,743	788,224	1,349,919	1,395,607
Retail \| Operating Segments \| Deckorators
Revenue
Total Net Sales	122,678	97,994	191,347	163,606
Retail \| Operating Segments \| ProWood
Revenue
Total Net Sales	669,050	657,098	1,109,799	1,171,376
Packaging \| Operating Segments
Revenue
Total Net Sales	458,245	428,669	852,338	838,677
Packaging \| Operating Segments \| Structural Packaging
Revenue
Total Net Sales	282,305	267,301	531,598	523,283
Packaging \| Operating Segments \| PalletOne
Revenue
Total Net Sales	153,897	141,914	278,083	276,133
Packaging \| Operating Segments \| Protective Packaging
Revenue
Total Net Sales	22,043	19,454	42,657	39,261
Construction \| Operating Segments
Revenue
Total Net Sales	526,777	551,590	992,290	1,067,530
Construction \| Operating Segments \| Factory Built
Revenue
Total Net Sales	215,545	229,669	408,929	446,888
Construction \| Operating Segments \| Site-Built
Revenue
Total Net Sales	186,405	202,413	337,275	393,030
Construction \| Operating Segments \| Commercial
Revenue
Total Net Sales	71,370	70,515	144,613	134,235
Construction \| Operating Segments \| Concrete Forming
Revenue
Total Net Sales	53,457	48,993	101,473	93,377
All Other \| Operating Segments
Revenue
Total Net Sales	$ 76,927	$ 65,026	$ 145,432	$ 125,324