Refers to an additional period of time to issue notes.

No definition available.

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Balance Type:	na
Period Type:	duration

- Definition

Represents the restrictions on investments, change of control provisions and provisions, expressed as a percentage of total assets to be disposed off as per the financial covenant.

+ References

No definition available.

+ Details

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the number of tranches related to issuance of debt.

+ References

No definition available.

+ Details

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Namespace Prefix:	prim_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

The period of time specific payments are to be made per the agreement.

+ References

No definition available.

+ Details

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Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the amount of prepayment to be paid on the debt instrument.

+ References

No definition available.

+ Details

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Namespace Prefix:	prim_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Represents the percentage of debt outstanding in which the interest rate was effectively exchanged

+ References

No definition available.

+ Details

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Namespace Prefix:	prim_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The annual fee percentage based on any issued and outstanding letters of credit under the facility.

+ References

No definition available.

+ Details

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility with the accordion feature.

+ References

No definition available.

+ Details

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Namespace Prefix:	prim_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The amount that the debt instrument can increase per the accordian feature.

+ References

No definition available.

+ Details

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Namespace Prefix:	prim_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of the total principal payments made during the annual reporting period.

+ References

+ Details

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

- Definition

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

+ References

No definition available.

+ Details

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

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
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-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

+ Details

Name:	us-gaap_DebtInstrumentFaceAmount
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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

+ Details

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Data Type:	num:percentItemType
Balance Type:	na
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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Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of the required periodic payments applied to principal.

+ References

+ Details

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

- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Weighted average interest rate of debt outstanding.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount, before 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 835
-SubTopic 30
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28555-108399

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

- Definition

Fixed interest rate related to the interest rate derivative.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

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

+ References

No definition available.

+ Details

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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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
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-Paragraph 1
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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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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

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of cash outflow for cost from early extinguishment and prepayment of debt. Includes, but is not limited to, third-party cost, premium paid, and other fee paid to lender directly for debt extinguishment or debt prepayment. Excludes accrued interest.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3291-108585

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

- Details

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- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_SeniorNotesMember
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- Details

Name:	us-gaap_LongtermDebtTypeAxis=prim_PrivateShelfAgreementMember
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Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_SecuredDebtMember
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Name:	us-gaap_CreditFacilityAxis=us-gaap_LoansPayableMember
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Credit Arrangements - Narrative (Details) $ in Thousands, $ in Millions			3 Months Ended	9 Months Ended	12 Months Ended	34 Months Ended
	Aug. 03, 2018 USD ($)	Jun. 03, 2015 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2018 CAD ($)	Dec. 31, 2019 USD ($)	Nov. 09, 2015 USD ($) item	Dec. 31, 2019 CAD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 CAD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 29, 2017 USD ($)	Sep. 28, 2017 USD ($)	Jul. 25, 2013 USD ($)	Dec. 28, 2012 USD ($)
Credit arrangements
Weighted average interest rate (as a percent)							4.00%	4.00%	4.10%
Mortgages \| Minimum
Credit arrangements
Interest rate (as a percent)							4.30%	4.30%
Mortgages \| Maximum
Credit arrangements
Interest rate (as a percent)							5.00%	5.00%
Senior secured notes
Credit arrangements
Interest rate (as a percent)						4.60%								3.85%	3.65%
Principal amount						$ 25,000								$ 25,000	$ 50,000
Number of tranches \| item						3
Prepayment penalty			$ 2,300
Notes Agreement
Credit arrangements
Principal amount															$ 25,000
Notes Agreement \| Minimum
Credit arrangements
Restrictions on investments, change of control provisions and provisions as a percentage of total assets to be disposed off					20.00%
Notes Agreement \| Maximum
Credit arrangements
Principal amount		$ 75,000
Commercial Equipment Notes \| Minimum
Credit arrangements
Interest rate (as a percent)							1.83%	1.83%
Commercial Equipment Notes \| Maximum
Credit arrangements
Interest rate (as a percent)							4.40%	4.40%
Credit Agreement
Credit arrangements
Maximum borrowing capacity												$ 200,000	$ 125,000
Potential increase per the agreement	$ 75,000
Debt issuance costs										$ 1,000	$ 600
Borrowings outstanding								$ 0
Additional Period to Issue Notes		3 years
Available borrowing capacity								164,200
Credit Agreement \| Federal funds rate
Credit arrangements
Basis spread on variable rate (as a percent)					0.50%
Credit Agreement \| Minimum
Credit arrangements
Prepayment to be paid on debt					$ 5,000
Restrictions on investments, change of control provisions and provisions as a percentage of total assets to be disposed off					20.00%
Credit Agreement \| Revolving Credit Facility
Credit arrangements
Maximum borrowing capacity								200,000
Maximum borrowing capacity with accordion feature								250,000
Credit Agreement \| Commercial letters of credit
Credit arrangements
Letters of credit outstanding								$ 35,800
Term Loan
Credit arrangements
Principal amount	220,000
Interest rate swap agreement				75.00%
Derivative fixed interest rate (as a percent)				2.886%						2.886%
Term Loan \| LIBOR
Credit arrangements
Basis spread on variable rate (as a percent)					1.75%
Term Loan \| First Three Years
Credit arrangements
Quarterly principal payment	2,750
Annual principal payments	$ 11,000
Number of years payments are to be made	3 years
Term Loan \| Next Two Years
Credit arrangements
Quarterly principal payment	$ 4,125
Annual principal payments	$ 16,500
Canadian Credit Facility
Credit arrangements
Available borrowing capacity							$ 3.4
Canadian Credit Facility \| Commercial letters of credit
Credit arrangements
Maximum borrowing capacity				$ 8.0					$ 4.0
Letters of credit outstanding							$ 0.6
Annual fee (as a percent)					1.00%
Canadian Credit Facility \| Commercial letters of credit \| Maximum
Credit arrangements
Term of credit facility					5 years