Weighted average interest rate of debt outstanding.

No definition available.

Name:	us-gaap_DebtWeightedAverageInterestRate
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of the cost of borrowed funds accounted for as interest expense.

+ References

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-Topic 835
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+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

Name:	us-gaap_LettersOfCreditOutstandingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

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-Publisher FASB
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-Topic 210
-SubTopic 10
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+ Details

Name:	us-gaap_LineOfCredit
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_LineOfCreditFacilityLineItems
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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_RevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_LineOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=spxc_SeniorCreditFacilitiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_LetterOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=spxc_BilateralForeignCreditInstrumentFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_DomesticLineOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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INDEBTEDNESS - Senior Credit Facilities (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jul. 03, 2021	Jun. 27, 2020	Jul. 03, 2021	Jun. 27, 2020	May 24, 2021
Line of Credit Facility [Line Items]
Interest expense	$ 3,400,000	$ 4,800,000	$ 7,600,000	$ 9,500,000
Revolving loans
Line of Credit Facility [Line Items]
Interest expense	$ 200,000		$ 200,000
Line of Credit
Line of Credit Facility [Line Items]
Weighted-average interest rate of senior credit facilities (as a percent)	1.50%		1.50%
Line of Credit \| Senior Credit Facilities \| Revolving loans
Line of Credit Facility [Line Items]
Maximum borrowing capacity					$ 20,000,000.0
Letter of Credit \| Bilateral Foreign Credit Instrument Facility \| Revolving loans
Line of Credit Facility [Line Items]
Maximum borrowing capacity					$ 25,000,000.0
Domestic Line of Credit
Line of Credit Facility [Line Items]
Amount of available borrowing capacity	$ 297,800,000		$ 297,800,000
Borrowings under line of credit	140,000,000.0		140,000,000.0
Letters of credit issued, amount outstanding	12,200,000		12,200,000
Foreign credit instrument facility
Line of Credit Facility [Line Items]
Amount of available borrowing capacity	28,800,000		28,800,000
Letters of credit issued, amount outstanding	$ 26,200,000		$ 26,200,000