Employee Benefit Plans - Obligations and Funded Status Narrative (Details) $ in Millions	Dec. 31, 2021 USD ($)
Pension plans
Employee benefit plans
Non-funded plan, current underfunded status	$ 60.4

The unfunded status is measured as the difference between the benefit obligation and the fair value of plan assets. Unfunded plans may include foreign pension plans and may also include other postretirement benefit plans.

No definition available.

Name:	spxc_DefinedBenefitPlanUnfundedStatusOfPlan
Namespace Prefix:	spxc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant