CONTINGENT LIABILITIES AND OTHER MATTERS - Environmental Matters (Details) - Site investigation and remediation - site	Sep. 26, 2020	Dec. 31, 2019
Environmental Matters
Number of sites	25	29
Number of third-party disposal sites for which entity is potentially responsible	14
Number of active sites	9

Represents the number of offsite, third-party disposal sites for which the entity is potentially responsible and have received notices of potential liability pursuant to various environmental laws.

No definition available.

Name:	spxc_SiteContingencyNumberOfSitesOnWhichEntityPotentiallyResponsible
Namespace Prefix:	spxc_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant