Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement [Abstract]
Revenues	$ 1,425.8	$ 1,472.3	$ 1,559.0
Costs and expenses:
Cost of products sold	1,095.6	1,096.5	1,283.1
Selling, general and administrative	282.3	301.0	387.8
Intangible amortization	0.6	2.8	5.2
Impairment of intangible assets	0.0	30.1	0.0
Special charges, net	2.7	5.3	5.1
Gain on contract settlement	10.2	0.0	0.0
Gain on sale of dry cooling business	0.0	18.4	0.0
Operating income (loss)	54.8	55.0	(122.2)
Other expense, net	(2.0)	(0.3)	(10.0)
Interest expense	(17.1)	(14.8)	(22.0)
Interest income	1.3	0.8	1.3
Loss on amendment/refinancing of senior credit agreement	(0.9)	(1.3)	(1.4)
Income (loss) from continuing operations before income taxes	36.1	39.4	(154.3)
Income tax (provision) benefit	47.9	(9.1)	2.7
Income (loss) from continuing operations	84.0	30.3	(151.6)
Income (loss) from discontinued operations, net of tax	0.0	(16.6)	39.8
Gain (loss) on disposition of discontinued operations, net of tax	5.3	(81.3)	(5.2)
Income (loss) from discontinued operations, net of tax	5.3	(97.9)	34.6
Net income (loss)	89.3	(67.6)	(117.0)
Less: Net loss attributable to noncontrolling interests	0.0	(0.4)	(34.3)
Net income (loss) attributable to SPX Corporation common shareholders	89.3	(67.2)	(82.7)
Adjustment related to redeemable noncontrolling interest (Note 13)	0.0	(18.1)	0.0
Net income (loss) attributable to SPX Corporation common shareholders after adjustment related to redeemable noncontrolling interest	89.3	(85.3)	(82.7)
Amounts attributable to SPX Corporation common shareholders after adjustment related to redeemable noncontrolling interest:
Income (loss) from continuing operations, net of tax	84.0	12.6	(118.2)
Income (loss) from discontinued operations, net of tax	5.3	(97.9)	35.5
Net income (loss) attributable to SPX Corporation common shareholders after adjustment related to redeemable noncontrolling interest	$ 89.3	$ (85.3)	$ (82.7)
Basic income (loss) per share of common stock:
Income (loss) from continuing operations attributable to SPX Corporation common shareholders after adjustment related to redeemable noncontrolling interest (in dollars per share)	$ 1.98	$ 0.30	$ (2.90)
Income (loss) from discontinued operations attributable to SPX Corporation common shareholders (in dollars per share)	0.13	(2.35)	0.87
Net income (loss) per share attributable to SPX Corporation common shareholders after adjustment related to redeemable noncontrolling interest (in dollars per share)	$ 2.11	$ (2.05)	$ (2.03)
Weighted-average number of common shares outstanding — basic (in shares)	42,413	41,610	40,733
Diluted income (loss) per share of common stock:
Income (loss) from continuing operations attributable to SPX Corporation common shareholders after adjustment related to redeemable noncontrolling interest (in dollars per share)	$ 1.91	$ 0.30	$ (2.90)
Income (loss) from discontinued operations attributable to SPX Corporation common shareholders (in dollars per share)	0.12	(2.32)	0.87
Net income (loss) per share attributable to SPX Corporation common shareholders after adjustment related to redeemable noncontrolling interest (in dollars per share)	$ 2.03	$ (2.02)	$ (2.03)
Weighted-average number of common shares outstanding — diluted (in shares)	43,905	42,161	40,733