Shareholders' Equity and Stock-Based Compensation (Details) (USD $) In Millions, except Share data in Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 29, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Oct. 01, 2011	Jul. 02, 2011	Apr. 02, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Numerator:
Income (loss) from continuing operations	$ (179.2)	$ 54.1	$ 38.5	$ 8.2	$ 58.5	$ 50.8	$ 25.5	$ 20.8	$ (78.4)	$ 155.6	$ 178.0
Less: Net income (loss) attributable to noncontrolling interests									2.8	5.0	(2.8)
Income (loss) from continuing operations attributable to SPX Corporation common shareholders for calculating basic and diluted earnings per share									(81.2)	150.6	180.8
Income from discontinued operations	320.0	6.1	9.7	4.6	5.0	11.5	9.5	4.0	340.4	30.0	24.8
Income from discontinued operations attributable to SPX Corporation common shareholders for calculating basic and diluted earnings per share									$ 340.4	$ 30.0	$ 24.8
Denominator:
Weighted-average number of common shares used in basic earnings per share									50,031	50,499	49,718
Dilutive securities - Employee stock options and restricted stock units										447	629
Weighted-average number of common and dilutive securities used for calculating diluted income per share									50,031	50,946	50,347
Stock options
Stock-Based Compensation
The number of options or units that were excluded from the computation of diluted earnings per share (in shares)									3	117	405
Restricted stock and restricted stock units
Stock-Based Compensation
The number of options or units that were excluded from the computation of diluted earnings per share (in shares)									1,031	633	102