Summary of Significant Accounting Policies and Other Information - Schedule of Product Warranty Liability (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2020	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Accrued Product Warranty
Balance at beginning of period		$ 25,501	$ 23,102
Current year provision		7,418	4,585
Changes in estimates for preexisting warranties	$ 9,300	9,925	2,730
Payments made during the period		(10,373)	(4,454)
Balance at end of period	32,471	32,471	25,963
Less: Current portion	16,660	16,660	15,078	$ 17,142
Noncurrent accrued product warranty	$ 15,811	$ 15,811	$ 10,885
Diluted share (in dollars per share)	$ 0.41	$ 0.43	$ 0.13

Standard Product Warranty Accrual, Earnings Per Share, Diluted

No definition available.

Name:	psix_StandardProductWarrantyAccrualEarningsPerShareDiluted
Namespace Prefix:	psix_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

+ Details

Name:	us-gaap_MovementInStandardProductWarrantyAccrualRollForward
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount as of the balance sheet date of the aggregate standard product warranty liability. Does not include the balance for the extended product warranty liability.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 8
-Subparagraph (c)(1),(c)(5)
-URI http://asc.fasb.org/extlink&oid=68068213&loc=d3e12565-110249

+ Details

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

- Definition

Amount as of the balance sheet date of the aggregate standard product warranty liability that is expected to be paid within one year or the normal operating cycle, if longer. Does not include the balance for the extended product warranty liability.

+ References

No definition available.

+ Details

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

- Definition

Amount as of the balance sheet date of the aggregate standard product warranty liability that is expected to be paid after one year or beyond the normal operating cycle, if longer. Does not include the balance for the extended product warranty liability.

+ References

No definition available.

+ Details

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

- Definition

Amount of decrease in the standard product warranty accrual from payments made in cash or in kind to satisfy claims under the terms of the standard product warranty. Excludes extended product warranties.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 8
-Subparagraph ((c)(2))
-URI http://asc.fasb.org/extlink&oid=68068213&loc=d3e12565-110249

+ Details

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

- Definition

Amount of increase (decrease) in the standard product warranty accrual from changes in estimates attributable to preexisting product warranties. Excludes extended product warranties.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 8
-Subparagraph ((c)(4))
-URI http://asc.fasb.org/extlink&oid=68068213&loc=d3e12565-110249

+ Details

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

- Definition

Amount of increase in the standard product warranty accrual from warranties issued. Excludes extended product warranties.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 8
-Subparagraph ((c)(3))
-URI http://asc.fasb.org/extlink&oid=68068213&loc=d3e12565-110249

+ Details

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