XML 100 R83.htm IDEA: XBRL DOCUMENT
v3.20.4

Retirement Benefits - Narrative (Details) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2020 USD ($) employee | Dec. 31, 2019 USD ($) | Dec. 31, 2018 USD ($)
Defined Contribution Plan Disclosure [Line Items] |  |  |
Employer matching contributions | $ | $ 3,250 | $ 2,842 | $ 2,700
Number of employees | 2,600 |  |
Entity number of employees, field personnel | 2,200 |  |
Union Members |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |
Number of employees | 300 |  |
Number of employees, percent | 13.00% |  |

X
- Definition Number of persons employed by the Entity + References No definition available. + Details
Name: | dei_EntityNumberOfEmployees
Namespace Prefix: | dei_
Data Type: | xbrli:decimalItemType
Balance Type: | na
Period Type: | instant

X
- Definition Entity Number of Employees, Field Personnel + References No definition available. + Details
Name: | strl_EntityNumberofEmployeesFieldPersonnel
Namespace Prefix: | strl_
Data Type: | xbrli:decimalItemType
Balance Type: | na
Period Type: | instant

X
- Definition The percentage of the number of employees. + References No definition available. + Details
Name: | strl_NumberOfEmployeesPercent
Namespace Prefix: | strl_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- 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
Name: | us-gaap_DefinedContributionPlanDisclosureLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of discretionary contributions made by an employer to a defined contribution plan. + References No definition available. + Details
Name: | us-gaap_DefinedContributionPlanEmployerDiscretionaryContributionAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | srt_TitleOfIndividualAxis=strl_UnionMembersMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |