Contingent Liabilities and Other Matters - Executive Agreements (Details) - Executive officers	12 Months Ended
Dec. 31, 2021 officer
Executive Agreements
Period of rolling term of employment agreements	1 year
Number of executive officers with severance benefit agreements	6

Supplemental Unemployment Benefits, Number of Individuals with Severance Benefit Agreements

No definition available.

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