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Construction Joint Ventures - SEMA Financials (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule of Equity Method Investments [Line Items]
Revenues	$ 346,544	$ 291,699	$ 264,086	$ 223,949	$ 255,175	$ 291,266	$ 268,734	$ 222,492	$ 1,126,278	$ 1,037,667	$ 957,958
Operating income	9,732	12,115	11,184	4,720	9,410	14,373	12,149	6,679	37,751	42,611	26,176
Net income attributable to Sterling common stockholders	$ 22,301	$ 7,957	$ 7,828	$ 1,815	$ 5,607	$ 8,917	$ 8,174	$ 2,489	$ 39,901	$ 25,187	$ 11,617
RLW | Joint Ventures
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	51.00%								51.00%
SEMA Construction Inc | Joint Ventures
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	49.00%								49.00%
Revenues									$ 6,903
Operating income									467
Net income attributable to Sterling common stockholders									$ 471

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