CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME (LOSS) - USD ($) shares in Thousands, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 26, 2015	Sep. 27, 2014	Sep. 26, 2015	Sep. 27, 2014
Income Statement [Abstract]
Revenues	$ 374.1	$ 489.6	$ 1,209.8	$ 1,397.1
Costs and expenses:
Cost of products sold	371.2	377.1	1,036.4	1,082.8
Selling, general and administrative	106.8	111.9	322.4	366.8
Intangible amortization	1.3	1.4	3.9	4.3
Special charges, net	8.4	1.3	14.0	5.7
Operating loss	(113.6)	(2.1)	(166.9)	(62.5)
Other income (expense), net	(4.6)	(0.9)	(7.5)	488.5
Interest expense	(6.3)	(5.0)	(18.5)	(17.6)
Interest income	0.4	1.1	1.3	2.7
Loss on early extinguishment of debt	(1.4)	0.0	(1.4)	(32.5)
Equity earnings in joint ventures	0.3	0.3	0.8	0.8
Income (loss) from continuing operations before income taxes	(125.2)	(6.6)	(192.2)	379.4
Income tax (provision) benefit	(5.5)	(5.6)	8.6	(161.9)
Income (loss) from continuing operations	(130.7)	(12.2)	(183.6)	217.5
Income from discontinued operations, net of tax	0.7	78.7	80.8	199.2
Gain (loss) on disposition of discontinued operations, net of tax	(0.6)	(2.9)	(1.5)	12.0
Income 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
Amounts attributable to SPX Corporation common shareholders:
Income (loss) from continuing operations, net of tax	(105.1)	(11.8)	(153.4)	219.8
Income from discontinued operations, net of tax	0.1	75.1	80.2	210.2
Net income (loss)	$ (105.0)	$ 63.3	$ (73.2)	$ 430.0
Basic income (loss) per share of common stock:
Income (loss) from continuing operations attributable to SPX Corporation common shareholders	$ (2.58)	$ (0.28)	$ (3.78)	$ 5.11
Income from discontinued operations attributable to SPX Corporation common shareholders	0.00	1.79	1.98	4.88
Net income (loss) per share attributable to SPX Corporation common shareholders	$ (2.58)	$ 1.51	$ (1.80)	$ 9.99
Weighted-average number of common shares outstanding — basic	40,663	41,796	40,590	43,024
Diluted income (loss) per share of common stock:
Income (loss) from continuing operations attributable to SPX Corporation common shareholders	$ (2.58)	$ (0.28)	$ (3.78)	$ 5.02
Income from discontinued operations attributable to SPX Corporation common shareholders	0.00	1.79	1.98	4.80
Net income (loss) per share attributable to SPX Corporation common shareholders	$ (2.58)	$ 1.51	$ (1.80)	$ 9.82
Weighted-average number of common shares outstanding — diluted	40,663	41,796	40,590	43,772
Comprehensive income (loss)	$ (170.5)	$ (52.3)	$ (233.7)	$ 310.6