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

- Details

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

The amount of the cost recognized during the period for defined contribution plans.

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=6414718&loc=d3e28014-114942

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 11

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.