Debt Instrument, Extension Fee

No definition available.

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Period Type:	duration

- Definition

Line Of Credit Facility, Number Of Days To Submit Borrowing Request

+ References

No definition available.

+ Details

Name:	psix_LineOfCreditFacilityNumberOfDaysToSubmitBorrowingRequest
Namespace Prefix:	psix_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Line of Credit Facility, Expiration Period Prior To Final Maturity Of Senior Notes

+ References

No definition available.

+ Details

Name:	psix_LineofCreditFacilityExpirationPeriodPriorToFinalMaturityOfSeniorNotes
Namespace Prefix:	psix_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Decrease for amounts of indebtedness forgiven by the holder of the debt instrument.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(f))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- 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

Amount, before accumulated amortization, of debt issuance costs related to line of credit arrangements. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section S45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=68176171&loc=SL68176184-208336

+ Details

Name:	us-gaap_DebtIssuanceCostsLineOfCreditArrangementsGross
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

+ 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 210.5-02.17)
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-URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28555-108399

+ Details

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

- Definition

Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 50
-Section 40
-Paragraph 4
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-Subparagraph (b)
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+ Details

Name:	us-gaap_GainsLossesOnExtinguishmentOfDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 6
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=120520924&loc=SL6036836-161870

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-URI http://asc.fasb.org/extlink&oid=120395209&loc=SL114868664-224227

+ Details

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

- Definition

Amount of current borrowing capacity under the credit facility considering any current restrictions on the amount that could be borrowed (for example, borrowings may be limited by the amount of current assets), but without considering any amounts currently outstanding under the facility.

+ References

+ Details

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

- 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

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

- Definition

The cash outflow during the period from the repayment of aggregate short-term and long-term debt. Excludes payment of capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3291-108585

+ Details

Name:	us-gaap_RepaymentsOfDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_SeniorNotesMember
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- Details

Name:	us-gaap_DebtInstrumentAxis=psix_FivePointFiveZeroPercentSeniorNotesMember
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Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_RevolvingCreditFacilityMember
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- Details

Name:	us-gaap_DebtInstrumentAxis=psix_StandardCharteredBankCreditAgreementMember
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Balance Type:
Period Type:

- Details

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- Details

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- Details

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- Details

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Debt - Narrative (Details)				3 Months Ended		12 Months Ended
Debt - Narrative (Details)	Mar. 26, 2021 USD ($) d	Dec. 28, 2020 USD ($)	Apr. 02, 2020 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Debt Instrument [Line Items]
Interest paid						$ 4,200,000	$ 6,900,000
Loss on extinguishment of debt				$ 497,000	$ 0	497,000	0
Debt issuance costs				$ 1,100,000	$ 300,000	$ 1,100,000	$ 300,000
Unsecured senior notes \| 5.50% Senior Notes
Debt Instrument [Line Items]
Redemption and discharge of debt			$ 55,000,000.0
Revolving credit facility \| Standard Chartered Bank Credit Agreement
Debt Instrument [Line Items]
Maturity period prior to the final maturity			60 days
Extension fee			0.25%
Basis spread on variable rate			0.25%
Borrowing amount			$ 95,000,000.0
Loss on extinguishment of debt			500,000
Debt issuance costs			$ 2,000,000.0
Revolving credit facility \| Standard Chartered Bank Credit Agreement \| Subsequent Event
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 130,000,000.0
Credit agreement fees	$ 1,900,000
Revolving credit facility \| Standard Chartered Bank Credit Agreement \| LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate			2.00%
Revolving credit facility \| Standard Chartered Bank Credit Agreement \| LIBOR \| Subsequent Event
Debt Instrument [Line Items]
Basis spread on variable rate	2.70%
Revolving credit facility \| Wells Fargo Credit Agreement
Debt Instrument [Line Items]
Repayment of debt			$ 16,800,000
Revolving credit facility \| Shareholder's Loan Agreement, Weichai
Debt Instrument [Line Items]
Maximum borrowing capacity		$ 100,000,000.0
Basis spread on variable rate		3.50%
Revolving credit facility \| Shareholder's Loan Agreement, Weichai \| Subsequent Event
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 130,000,000.0
Number of days to submit borrowing request \| d	5
Revolving credit facility \| Shareholder's Loan Agreement, Weichai \| LIBOR \| Subsequent Event
Debt Instrument [Line Items]
Basis spread on variable rate	4.50%