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Business Segments - Narrative (Details) $ in Millions	12 Months Ended
Business Segments - Narrative (Details) $ in Millions	Dec. 28, 2025 USD ($) segment	Dec. 29, 2024 USD ($)	Dec. 31, 2023 USD ($)	Jan. 01, 2023 USD ($)
Segment Reporting Information [Line Items]
Number of operating segments \| segment	2
Number of reportable segments \| segment	2
Total international sales	$ 1,947.6	$ 1,836.9	$ 1,922.9
Sales by U.S. operations to foreign countries	1,562.5	1,425.4	1,498.7
Income from government assistance, CARES Act	7.2	16.7		$ 34.0
Selling and administrative expenses	365.1	342.3	328.1
Gains from disposal of property, plant and equipment, net	10.5	11.6	0.3
Gain (loss) on sales of business, net	(2.9)	52.9	(0.6)
Depreciation of property, plant and equipment	146.6	118.8	117.4
Proceeds from divestiture of businesses, net of cash divested	26.8	48.0	(0.3)
Facility Closing
Segment Reporting Information [Line Items]
Depreciation of property, plant and equipment			3.8
Houston, PA facility
Segment Reporting Information [Line Items]
Gain (loss) on sales of business, net		2.3
Proceeds from sale of other assets		3.5
East Hartford, CT \| Disposal Group, Disposed of by Sale, Not Discontinued Operations
Segment Reporting Information [Line Items]
Gain (loss) on sale of businesses	0.8
Proceeds from sales of businesses, net of transaction costs	19.3
Birmingham, UK and Dusseldorf, Germany \| Disposal Group, Disposed of by Sale, Not Discontinued Operations
Segment Reporting Information [Line Items]
Gain (loss) on sale of businesses	(3.7)
Proceeds from sales of businesses, net of transaction costs	5.0
Expected consideration expected to be collected in next 12 months	4.9
New Bedford, MA and Remscheid, Germany \| Disposal Group, Disposed of by Sale, Not Discontinued Operations
Segment Reporting Information [Line Items]
Gain (loss) on sale of businesses		52.9
Proceeds from sales of businesses, net of transaction costs	$ 2.5	48.0
Operating Segments \| Commercial Negotiations With a Customer
Segment Reporting Information [Line Items]
Selling and administrative expenses		11.8
Allegheny Technologies Inc \| STAL Precision Stainless Steel Company Limited
Segment Reporting Information [Line Items]
Joint venture ownership percentage	60.00%
HPMC
Segment Reporting Information [Line Items]
Employee retention credits, aviation manufacturing jobs protection program	$ 4.4
HPMC \| Operating Segments \| Commercial Negotiations With a Customer
Segment Reporting Information [Line Items]
Selling and administrative expenses		6.3
AA&S
Segment Reporting Information [Line Items]
Employee retention credits, aviation manufacturing jobs protection program	$ 2.8
AA&S \| Operating Segments
Segment Reporting Information [Line Items]
Tax benefits		22.7	$ 10.1
AA&S \| Operating Segments \| Commercial Negotiations With a Customer
Segment Reporting Information [Line Items]
Selling and administrative expenses		$ 5.5
Revenue Benchmark \| Aerospace & Defense Market Concentration Risk \| HPMC
Segment Reporting Information [Line Items]
Percentage of sales	92.00%
Revenue Benchmark \| Commercial Jet Engines Concentration \| HPMC
Segment Reporting Information [Line Items]
Percentage of sales	68.00%
Revenue Benchmark \| Defense Market Concentration \| HPMC
Segment Reporting Information [Line Items]
Percentage of sales	11.00%