Acquisitions and Discontinued Operations - Pre-tax Income (Loss) and After-tax Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended
Apr. 03, 2021	Mar. 28, 2020
Business Acquisition [Line Items]
Income from discontinued operations, net of tax	$ (0.8)	$ 0.0
Discontinued Operations \| SPX Heat Transfer Business
Business Acquisition [Line Items]
Revenues		1.9
Cost of product sold		1.5
Income before income tax		0.4
Income tax provision		0.0
Income from discontinued operations, net of tax		$ 0.4
Discontinued Operations, Disposed of by Sale
Business Acquisition [Line Items]
Income from discontinued operations, net of tax	$ (0.8)

Amount before tax of income (loss) from a discontinued operation. Includes, but is not limited to, the income (loss) from operations during the phase-out period, gain (loss) on disposal, gain (loss) for reversal of write-down (write-down) to fair value, less cost to sell, and adjustments to a prior period gain (loss) on disposal.

Amount of tax expense (benefit) related to a discontinued operation. Includes, but is not limited to, tax expense (benefit) related to income (loss) from operations during the phase-out period, tax expense (benefit) related to gain (loss) on disposal, tax expense (benefit) related to gain (loss) for reversal of write-down (write-down) to fair value, less cost to sell, and tax expense (benefit) related to adjustments of a prior period gain (loss) on disposal.

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+ Details