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v3.19.3.a.u2

Basis of Presentation and Summary of Significant Accounting Policies - Revenue Recognition (Details) $ in Millions | 12 Months Ended
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Dec. 31, 2017 USD ($)
Accounting Policies [Abstract] |
Revenue under percentage of completion | $ 255.5

X
- Definition Represents the revenue recognized during the period using the percentage-of-completion method. + References No definition available. + Details
Name: | spxc_RevenueUnderPercentageOfCompletionMethod
Namespace Prefix: | spxc_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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- References No definition available. + Details
Name: | us-gaap_AccountingPoliciesAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration