Construction Joint Ventures - Income Statement Information (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Sterling’s noncontrolling interest:
Revenues			$ 3,409	$ 2,966
Joint Ventures
Schedule of Equity Method Investments [Line Items]
Revenues	$ 29,557	$ 27,703	89,010	61,210
Income before tax	1,728	(6,281)	7,324	(3,611)
Sterling’s noncontrolling interest:
Revenues	12,820	13,664	41,739	28,826
Income before tax	$ 858	$ (1,629)	$ 3,716	$ (358)

Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to noncontrolling interest.

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