INCOME TAXES - Undistributed Foreign Earnings (Details) $ in Millions	Dec. 31, 2019 USD ($)
Income Tax Disclosure [Abstract]
Provision undistributed accumulated earnings of foreign subsidiary	$ 4.1

Tax Cuts and Jobs Act of 2017, Incomplete Accounting, Provisional Withholding and State Tax Expense (Benefit)

No definition available.

Name:	spxf_TaxCutsAndJobsActOf2017IncompleteAccountingProvisionalWithholdingAndStateTaxExpenseBenefit
Namespace Prefix:	spxf_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant