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Note 15 - Employee Benefit Plans - Participation in Multiemployer Defined Benefit Pension Plan (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Multiemployer Plan, Period Contributions		$ 12,638	$ 14,534	$ 10,808
Pension Trust Fund for Operating Engineers Pension Plan [Member]
Pension Protection Act Certified Zone Status	[1]	Red	Red
Multiemployer Plan, Period Contributions		$ 2,145	$ 2,151	1,757
Surcharge Imposed		No
Laborers Pension Trust for Northern California [Member]
Pension Protection Act Certified Zone Status	[1]	Yellow	Yellow
Multiemployer Plan, Period Contributions		$ 1,059	$ 966	1,447
Surcharge Imposed		No
Carpenter Funds Administrative Office [Member]
Pension Protection Act Certified Zone Status	[1]	Red	Red
Multiemployer Plan, Period Contributions		$ 636	$ 842	1,015
Surcharge Imposed		No
Cement Mason Pension Trust Fund for Northern California [Member]
Pension Protection Act Certified Zone Status	[1]	Yellow	Yellow
Multiemployer Plan, Period Contributions		$ 311	$ 371	322
Surcharge Imposed		No
All Other Funds [Member]
Multiemployer Plan, Period Contributions		$ 8,487	$ 10,204	$ 6,267
[1] The most recent PPA zone status available in 2016 and 2015 is for the plan’s year-end during 2015 and 2014, respectively. The zone status is based on information that we received from the plan and is certified by the plan’s actuary. Among other factors, plans in the red zone are generally less than 65 percent funded, plans in the orange zone are less than 80 percent funded and have an Accumulated Funding Deficiency in the current year or projected into the next six years, plans in the yellow zone are less than 80 percent funded and plans in the green zone are at least 80 percent funded.

X

- Definition

Amount of contributions made to multiemployer plans by the employer. A multiemployer plan is a pension or postretirement benefit plan to which two or more unrelated employers contribute where assets contributed by one participating employer may be used to provide benefits to employees of other participating employers.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 80
-Section 50
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=65877416&loc=SL14450702-114947

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 80
-Section 50
-Paragraph 9
-URI http://asc.fasb.org/extlink&oid=65877416&loc=SL14450691-114947

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 80
-Section 50
-Paragraph 5
-Subparagraph (e)(1)
-URI http://asc.fasb.org/extlink&oid=65877416&loc=SL14450657-114947

+ Details

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

X

- Definition

Indicate the multiemployer plan's certified zone status as currently required by the Pension Protection Act of 2006 or a subsequent amendment thereof. The zone status categories are red (critical status), orange (seriously endangered), yellow (endangered), and green (none of the above). The acceptable values are "red", "orange", "yellow", "green", "other", and "NA". A multiemployer plan is a pension or postretirement benefit plan to which two or more unrelated employers contribute where assets contributed by one participating employer may be used to provide benefits to employees of other participating employers.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 80
-Section 50
-Paragraph 5
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=65877416&loc=SL14450657-114947

+ Details

Name:	us-gaap_MultiemployerPlansCertifiedZoneStatus
Namespace Prefix:	us-gaap_
Data Type:	us-types:zoneStatusItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Indicate whether the employer paid a surcharge to the pension or postretirement benefit plan to which two or more unrelated employers contribute where assets contributed by one participating employer may be used to provide benefits to employees of other participating employers. The acceptable values are "no", "yes", and "NA".

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 80
-Section 50
-Paragraph 5
-Subparagraph (f)(2)
-URI http://asc.fasb.org/extlink&oid=65877416&loc=SL14450657-114947

+ Details

Name:	us-gaap_MultiemployerPlansSurcharge
Namespace Prefix:	us-gaap_
Data Type:	us-types:surchargeItemType
Balance Type:	na
Period Type:	duration

X

- Details

Name:	us-gaap_MultiemployerPlanTypeAxis=strl_PensionTrustFundForOperatingEngineersPensionPlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_MultiemployerPlanTypeAxis=strl_LaborersPensionTrustForNorthernCaliforniaMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_MultiemployerPlanTypeAxis=strl_CarpenterFundsAdministrativeOfficeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_MultiemployerPlanTypeAxis=strl_CementMasonPensionTrustFundForNorthernCaliforniaMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_MultiemployerPlanTypeAxis=strl_AllOtherFundsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: