Construction Joint Ventures - SEMA Financials (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Schedule of Equity Method Investments [Line Items]
Revenues	$ 400,038	$ 264,086	$ 696,726	$ 488,035
Operating income	33,046	11,184	45,149	15,904
Net income attributable to Sterling common stockholders	$ 18,210	7,828	$ 21,325	9,643
RLW | Joint Ventures
Schedule of Equity Method Investments [Line Items]
Ownership percentage	51.00%		51.00%
SEMA Construction Inc | Joint Ventures
Schedule of Equity Method Investments [Line Items]
Ownership percentage	49.00%		49.00%
Revenues	$ 3,404	1,027	$ 7,468	1,629
Operating income	375	75	671	113
Net income attributable to Sterling common stockholders	$ 376	$ 75	$ 675	$ 113