RECONCILIATION OF PREVIOUSLY REPORTED AMOUNTS TO AMOUNTS REVISED AND RESTATED (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 26, 2015	Sep. 27, 2014	Sep. 26, 2015	Sep. 27, 2014	Dec. 31, 2014
Consolidated Statement of Operations:
Revenues	$ 374.1	$ 489.6	$ 1,209.8	$ 1,397.1
Gross Profit		112.5		314.3
Income (loss) from continuing operations, net of tax	(130.7)	(12.2)	(183.6)	217.5
Income (loss) from discontinued operations, net of tax	0.1	75.8	79.3	211.2
Net income (loss)	(130.6)	63.6	(104.3)	428.7
Less: Net income (loss) attributable to noncontrolling interests	(25.6)	0.3	(31.1)	(1.3)
Net income (loss) attributable to SPX Corporation common shareholders	$ (105.0)	$ 63.3	$ (73.2)	$ 430.0
Basic income per share of common stock attributable to SPX Corporation common shareholders	$ (2.58)	$ 1.51	$ (1.80)	$ 9.99
Diluted income per share of common stock attributable to SPX Corporation common shareholders	$ (2.58)	$ 1.51	$ (1.80)	$ 9.82
Assets
Intangibles, net	$ 164.2		$ 164.2		$ 169.2
Other assets	642.0		642.0		623.0
Liabilities
Deferred and other income taxes	57.0		57.0		69.1
Equity:
Retained earnings	910.1		910.1		2,628.6
Previously Reported
Consolidated Statement of Operations:
Revenues		$ 1,171.2		$ 3,443.4
Gross Profit		347.4		996.1
Income (loss) from continuing operations, net of tax		66.7		420.1
Income (loss) from discontinued operations, net of tax		(2.9)		11.5
Net income (loss)		63.8		431.6
Less: Net income (loss) attributable to noncontrolling interests		0.3		(1.3)
Net income (loss) attributable to SPX Corporation common shareholders		$ 63.5		$ 432.9
Basic income per share of common stock attributable to SPX Corporation common shareholders		$ 1.52		$ 10.06
Diluted income per share of common stock attributable to SPX Corporation common shareholders		$ 1.50		$ 9.89
Assets
Intangibles, net					831.0
Other assets					729.8
Liabilities
Deferred and other income taxes					294.9
Equity:
Retained earnings					2,637.8
Reclassification of Discontinued Operations | Discontinued operations
Consolidated Statement of Operations:
Revenues		$ (681.6)		$ (2,046.3)
Gross Profit		(234.9)		(681.8)
Income (loss) from continuing operations, net of tax		(78.7)		(199.7)
Income (loss) from discontinued operations, net of tax		78.7		199.7
Net income (loss)		0.0		0.0
Less: Net income (loss) attributable to noncontrolling interests		0.0		0.0
Net income (loss) attributable to SPX Corporation common shareholders		0.0		0.0
Assets
Intangibles, net					(659.3)
Other assets					(101.4)
Liabilities
Deferred and other income taxes					(227.1)
Correction of Prior Period Misstatement
Consolidated Statement of Operations:
Revenues		0.0		0.0
Gross Profit		0.0		0.0
Income (loss) from continuing operations, net of tax		(0.2)		(2.9)
Income (loss) from discontinued operations, net of tax		0.0		0.0
Net income (loss)		(0.2)		(2.9)
Less: Net income (loss) attributable to noncontrolling interests		0.0		0.0
Net income (loss) attributable to SPX Corporation common shareholders		$ (0.2)		$ (2.9)
Assets
Intangibles, net					(2.5)
Other assets					(5.4)
Liabilities
Deferred and other income taxes					1.3
Equity:
Retained earnings					$ (9.2)
Correction of Prior Period Misstatement | Understatement of Deferred Tax Liabilities
Equity:
Deferred tax liability adjustment	(4.3)		(4.3)
Correction of Prior Period Misstatement | Tax effect from Understatement of Impairment Charge and Improper Capitalization of Software Development Costs
Equity:
Deferred tax liability adjustment	$ (3.0)		$ (3.0)