Weighted average interest rate of debt outstanding.

No definition available.

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Balance Type:	na
Period Type:	instant

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (a)
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8736-108599

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
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-Subparagraph (210.5-03(11))
-URI http://asc.fasb.org/extlink&oid=123367319&loc=SL114868664-224227

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-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04.9)
-URI http://asc.fasb.org/extlink&oid=120399700&loc=SL114874048-224260

+ Details

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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

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

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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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

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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

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Namespace Prefix:
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Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_LineOfCreditMember
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Balance Type:
Period Type:

- Details

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

- Details

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Balance Type:
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- Details

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- Details

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INDEBTEDNESS - Senior Credit Facilities (Details) - USD ($)	3 Months Ended		9 Months Ended
	Oct. 02, 2021	Sep. 26, 2020	Oct. 02, 2021	Sep. 26, 2020	May 24, 2021
Line of Credit Facility [Line Items]
Interest expense	$ 3,500,000	$ 4,500,000	$ 11,100,000	$ 14,000,000.0
Revolving loans
Line of Credit Facility [Line Items]
Interest expense			$ 200,000
Line of Credit
Line of Credit Facility [Line Items]
Weighted-average interest rate of senior credit facilities	1.60%		1.60%
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	$ 437,800,000		$ 437,800,000
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	31,200,000		31,200,000
Letters of credit issued, amount outstanding	$ 23,800,000		$ 23,800,000