BASIS OF PRESENTATION (Details 2) - USD ($) $ in Millions	3 Months Ended			9 Months Ended		12 Months Ended
	Sep. 26, 2015	Dec. 31, 2014	Sep. 27, 2014	Sep. 26, 2015	Sep. 27, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Jun. 27, 2015	Jun. 28, 2014	Jan. 01, 2014
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Pre-tax income (loss) from continuing operations	$ (125.2)		$ (6.6)	$ (192.2)	$ 379.4
Income tax expense overstated (understated)	5.5		5.6	(8.6)	161.9
Retained earnings	(910.1)	$ (2,628.6)		(910.1)		$ (2,628.6)
Total SPX Corporation shareholders’ equity	(356.7)	(1,808.7)		(356.7)		(1,808.7)
Total equity	(319.1)	(1,811.9)	(2,047.6)	(319.1)	(2,047.6)	(1,811.9)	$ (2,167.3)				$ (1,749.9)	$ (2,249.0)
Income from continuing operations	130.7		12.2	183.6	(217.5)
Previously Unrecorded Income Tax Liabilities Associated with Intercompany Loans
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Deferred tax liability adjustment	4.3			$ 4.3
Income tax expense overstated (understated)						2.4	(1.2)			$ 3.1
Restatement Adjustment
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Retained earnings		9.2				9.2
Total equity		(9.2)				(9.2)	(4.7)				$ (9.2)	$ (7.4)
Income from continuing operations			0.2		2.9
Restatement Adjustment | Adjustment for Previously Capitalized Software that should have been Expensed due to Lack of Technological Feasibility
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Capitalized software development costs that should have been expensed when incurred	$ 5.4
Restatement Adjustment | Capitalization of Development Costs and Understatement of Impairment Charge
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Pre-tax income (loss) from continuing operations						3.4	$ 2.4	$ 1.2	$ 0.5	$ 0.4
Restatement Adjustment | Previously Unrecorded Income Tax Liabilities Associated with Intercompany Loans
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Retained earnings													$ 4.7
Total SPX Corporation shareholders’ equity													4.7
Total equity													$ 4.7
Income from continuing operations			0.2		2.9
Previously Reported
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Retained earnings		(2,637.8)				$ (2,637.8)
Income from continuing operations			$ (66.7)		$ (420.1)
Previously Reported | Adjustment for Impairment Charge to Trademarks | Trademarks with indefinite lives | Power segment
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Impairment charge		8.4
Actual | Adjustment for Impairment Charge to Trademarks | Trademarks with indefinite lives | Power segment
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Impairment charge		$ 10.9