Acquisitions and Discontinued Operations - Wind-Down of the Heat Transfer Business (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2021	Oct. 02, 2021	Jul. 03, 2021	Apr. 03, 2021	Dec. 31, 2020	Sep. 26, 2020	Jun. 27, 2020	Mar. 28, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Costs and expenses:
Gain (loss) from discontinued operations, net of tax	$ 2.0	$ 316.4	$ 44.2	$ 3.8	$ 5.3	$ 3.1	$ 8.2	$ 8.6	$ 366.4	$ 25.2	$ (11.0)
Discontinued operations
Costs and expenses:
Income from discontinued operations									409.2	35.8	(9.5)
Income tax (provision) benefit			$ (33.0)						(42.8)	(10.6)	(1.5)
Gain (loss) from discontinued operations, net of tax									366.4	25.2	(11.0)
Discontinued operations | SPX Heat Transfer Business
Discontinued Operations
Revenues										3.9	4.5
Costs and expenses:
Cost of products sold										3.1	6.1
Selling, general and administrative										0.1	0.9
Special charges (credits), net										0.4	(0.4)
Other income, net										0.0	0.3
Income from discontinued operations									(0.3)	0.3	(1.8)
Income tax (provision) benefit									0.0	(0.1)	0.4
Gain (loss) from discontinued operations, net of tax									$ (0.3)	$ 0.2	$ (1.4)