Segment Reporting - Schedule of Segment Reporting by Segment (Details) $ in Thousands	12 Months Ended
	Jan. 03, 2026 USD ($) segment	Dec. 28, 2024 USD ($)	Dec. 30, 2023 USD ($)
Segment Reporting [Abstract]
Number of reportable segments \| segment	1
Segment Reporting Information [Line Items]
Net sales	$ 2,954,007	$ 2,952,532	$ 3,136,381
Cost of sales	2,502,379	2,463,393	2,609,364
Selling, general, and administrative expense	381,109	365,532	355,819
Depreciation of property and equipment	35,400	34,600	27,800
Amortization of definite-lived intangible assets	4,500	3,900	4,200
Recognition of deferred gains on real estate	3,934	3,934	3,934
Interest income	17,326	27,805	20,908
Settlement of defined benefit pension plan	0	(2,481)	30,440
(Benefit) provision for income taxes	(90)	17,571	33,350
Consolidated net income	219	53,116	48,536
Reportable Segment
Segment Reporting Information [Line Items]
Consolidated net income	219	53,116	48,536
Operating Segments \| Reportable Segment
Segment Reporting Information [Line Items]
Net sales	2,954,007	2,952,532	3,136,381
Depreciation of property and equipment	35,424	34,576	27,846
Amortization of definite-lived intangible assets	4,481	3,912	4,197
Recognition of deferred gains on real estate	(3,934)	(3,934)	(3,934)
Interest expense	49,680	47,169	44,654
Interest income	(17,326)	(27,805)	(20,908)
Settlement of defined benefit pension plan	0	(2,481)	30,440
Other, net	2,065	1,483	7,017
(Benefit) provision for income taxes	(90)	17,571	33,350
Total segment expenses	2,953,788	2,899,416	3,087,845
Consolidated net income	219	53,116	48,536
Adjustments and reconciling items \| Reportable Segment
Segment Reporting Information [Line Items]
Consolidated net income	0	0	0
Cost of specialty products sold
Segment Reporting Information [Line Items]
Net sales	2,052,990	2,045,910	2,184,240
Cost of specialty products sold \| Operating Segments \| Reportable Segment
Segment Reporting Information [Line Items]
Cost of sales	1,683,997	1,648,285	1,763,446
Cost of structural products sold
Segment Reporting Information [Line Items]
Net sales	901,017	906,622	952,141
Cost of structural products sold \| Operating Segments \| Reportable Segment
Segment Reporting Information [Line Items]
Cost of sales	818,382	815,108	845,918
SG&A - delivery and logistics \| Operating Segments \| Reportable Segment
Segment Reporting Information [Line Items]
Selling, general, and administrative expense	165,878	154,293	152,313
SG&A - sales \| Operating Segments \| Reportable Segment
Segment Reporting Information [Line Items]
Selling, general, and administrative expense	73,480	68,620	67,274
SG&A - all other \| Operating Segments \| Reportable Segment
Segment Reporting Information [Line Items]
Selling, general, and administrative expense	$ 141,751	$ 142,619	$ 136,232

BlueLinx Holdings Inc. 10-K