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total foreign country sales from domicile operations

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For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

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The amount of expense recognized in the current period that reflects the allocation of the cost of tangible assets over the assets' useful lives. Includes production and non-production related depreciation.

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The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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Amount of gain (loss) on sale or disposal of other assets.

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Amount of gain (loss) from the difference between the sale price or salvage price and the book value of an asset that was sold or retired, and gain (loss) from the write down of assets from their carrying value to fair value.

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Business Segments - Narrative (Details) - USD ($) $ in Millions	3 Months Ended				12 Months Ended
	Oct. 01, 2023	Oct. 02, 2022	Jul. 03, 2022	Apr. 03, 2022	Dec. 31, 2023	Jan. 01, 2023	Jan. 02, 2022
Segment Reporting Information [Line Items]
Gain (loss) on asset sales and sale of business, net					$ (0.6)	$ (105.4)	$ 13.8
Proceeds from sales of businesses, net of transaction costs					(0.3)	0.3	53.1
Restructuring and other credits (charges)					(31.4)	(23.7)	10.5
Income (loss) from equity method investments					(1.6)	12.6	0.1
Total international sales					1,922.9	1,617.4	1,264.9
Sales by U.S. operations to foreign countries					1,498.7	1,217.9	846.3
Inventory valuation reserves					75.5	70.9
Closed operations and other income (expenses)					(13.3)	(5.6)	3.1
Net gain (loss) on sale of businesses					0.0	0.0	13.8
Income From Government Assistance, CARES Act						34.0
Restructuring charges	$ (0.5)	$ (2.6)	$ (1.3)	$ (1.1)
Asset Write-offs
Segment Reporting Information [Line Items]
Restructuring charges					10.3
Facility Closing
Segment Reporting Information [Line Items]
Depreciation					$ 3.8
Sheffield, UK Operations
Segment Reporting Information [Line Items]
Net gain (loss) on sale of businesses			$ (87.1)	(25.1)		(112.2)
Pico Rivera, CA Operations
Segment Reporting Information [Line Items]
Gain (Loss) on disposition of other assets				$ 6.8		6.8
High Performance Materials & Components
Segment Reporting Information [Line Items]
Employee Retention Credits, Aviation Manufacturing Jobs Protection Program						27.0
Advanced Alloys & Solutions [Member]
Segment Reporting Information [Line Items]
Employee retention credits						7.0
Allegheny & Tsingshan Stainless
Segment Reporting Information [Line Items]
Equity method investment ownership percentage					50.00%
Income (loss) from equity method investments					$ (1.8)	9.1	(0.9)
Allegheny & Tsingshan Stainless \| Advanced Alloys & Solutions [Member]
Segment Reporting Information [Line Items]
Income (loss) from equity method investments					$ (1.8)	8.2	(0.9)
Uniti [Member]
Segment Reporting Information [Line Items]
Equity method investment ownership percentage					50.00%
Uniti [Member] \| Advanced Alloys & Solutions [Member]
Segment Reporting Information [Line Items]
Income (loss) from equity method investments					$ 0.2	4.4	1.0
Operating Segments
Segment Reporting Information [Line Items]
Depreciation					$ 117.4	$ 115.4	$ 117.4
Aerospace & Defense Market Concentration Risk [Member] \| Revenue Benchmark [Member] \| High Performance Materials & Components
Segment Reporting Information [Line Items]
Percentage of sales					85.00%
Energy and Aerospace & Defense Market Concentration [Member] \| Revenue Benchmark [Member] \| Advanced Alloys & Solutions [Member]
Segment Reporting Information [Line Items]
Percentage of sales					60.00%
Commercial Jet Engines Concentration \| Revenue Benchmark [Member] \| High Performance Materials & Components
Segment Reporting Information [Line Items]
Percentage of sales					60.00%
Allegheny Technologies Inc \| STAL Precision Stainless Steel Company Limited [Member]
Segment Reporting Information [Line Items]
Joint venture ownership percentage					60.00%