Name:	prim_DefinedContributionPlanDPSPPortionVestingPeriodAsNumberOfYearsOfEmployment
Namespace Prefix:	prim_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Represents the second level of employee contributions (percentage of compensation) which are partially matched by the employer.

No definition available.

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

Represents the employer matching contribution of the first level of employee contributions.

No definition available.

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

Represents the employer matching contribution of the second level of employee contributions.

No definition available.

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

Represents the first level of employee contributions (percentage of compensation) which are matched by the employer.

No definition available.

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

- References

No definition available.

Name:	prim_DefinedContributionPlanLineItems
Namespace Prefix:	prim_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Represents the maximum contribution by eligible employees, as a percentage of their salary, subject to the annual limit prescribed by Internal Revenue Service.

No definition available.

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

Represents the number of components of the defined contribution plan.

No definition available.

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

Amount of cost for defined contribution plan.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 70
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=49170846&loc=d3e28014-114942

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

Amount of discretionary contributions made by an employer to a defined contribution plan.

No definition available.

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

Name:	us-gaap_RetirementPlanSponsorLocationAxis=country_US
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_RetirementPlanNameAxis=prim_UnitedStatesDefinedContributionPlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_RetirementPlanSponsorLocationAxis=country_CA
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: