Discontinued Operations and Other Dispositions - Consolidated Statements (Details) - USD ($) $ in Millions	3 Months Ended									12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jul. 01, 2017	Apr. 01, 2017	Dec. 31, 2016	Oct. 01, 2016	Jul. 02, 2016	Apr. 02, 2016	Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss from discontinued operations										$ 0.0	$ (16.6)	$ 39.8
Income before taxes										(6.6)	(110.7)	65.1
Income tax provision										11.9	12.8	(30.5)
Income (loss) from discontinued operations, net of tax	$ (1.4)	$ 0.3	$ (0.7)	$ 7.1	$ (83.1)	$ (4.7)	$ (3.5)	$ (6.6)		5.3	(97.9)	34.6
Less: Net loss attributable to noncontrolling interest										0.0	0.0	(0.9)
Income (loss) from discontinued operations attributable to SPX Corporation common shareholders for calculating basic and diluted income per share										5.3	(97.9)	35.5
SPX Flow, Inc | Discontinued Operations, Disposed of by Means Other than Sale, Spinoff
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Revenues												1,775.1
Costs of products sold												1,179.3
Selling, general and administrative												368.2
Intangible amortization												17.7
Special charges (credits), net												41.2
Other income (expense), net												1.3
Interest expense, net												(32.6)
Income before taxes										0.0	0.0	122.4
Income tax provision									$ (1.4)	0.0	0.0	(43.0)
Income (loss) from discontinued operations, net of tax										0.0	0.0	79.4
Less: Net loss attributable to noncontrolling interest												(0.9)
Income (loss) from discontinued operations attributable to SPX Corporation common shareholders for calculating basic and diluted income per share												80.3
Depreciation and amortization												44.3
Impairment of intangible assets												15.0
Capital expenditures												43.1
Professional fees and other costs incurred in connection with Spin Off												30.8
Balcke Durr | Discontinued Operations, Disposed of by Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Revenues											153.4	160.3
Costs of products sold											144.2	143.8
Selling, general and administrative											31.4	37.9
Impairment of intangible assets											0.0	13.7
Special charges (credits), net											(1.3)	12.7
Other expense											(0.2)	(0.9)
Loss before taxes											(21.1)	(48.7)
Income tax benefit										9.4	4.5	9.1
Loss from discontinued operations			$ 0.4	$ 7.2						6.8	(16.6)	(39.6)
Income before taxes										(2.6)	(107.0)	(48.7)
Income tax provision										9.4	11.8	9.1
Income (loss) from discontinued operations, net of tax										$ 6.8	(95.2)	(39.6)
Depreciation and amortization											2.0	2.2
Capital expenditures											$ 0.7	$ 1.9