Noncontrolling Interests (Details) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Sep. 30, 2018 USD ($) item	Sep. 30, 2018 USD ($) item	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) item	Sep. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)
Noncontrolling Interests
Number of joint ventures | item	2	2		2
Tax effect on income recognized		$ 10,716	$ 9,952	$ 14,633	$ 28,644
Revenue		908,902		2,061,808
Net income attributable to noncontrolling interests		2,114	1,537	8,118	3,209
Cash	$ 60,039	60,039		60,039		$ 170,385
Accounts receivable	473,045	473,045		473,045		291,589
Contract assets	382,492	382,492		382,492		265,902
Accounts payable	241,288	241,288		241,288		140,943
Contract liabilities	219,232	219,232		219,232		169,377
Carlsbad
Noncontrolling Interests
Revenue		18,415	28,722	89,672	65,725
Net income attributable to noncontrolling interests		2,101	550	7,545	930
Distributions to partners	5,000	5,000
Non-controlling interest distribution					0
Cash	14,992	14,992		14,992		44,308
Accounts receivable	109	109		109		15,343
Contract assets	12,620	12,620		12,620
Accounts payable	2,673	2,673		2,673		12,352
Contract liabilities	9,624	9,624		9,624		42,743
Due to Primoris	5,778	5,778		5,778
Carlsbad | Non Controlling Interest
Noncontrolling Interests
Distributions to partners	5,000	5,000
Wilmington
Noncontrolling Interests
Revenue			5,143	1,921	29,742
Net income attributable to noncontrolling interests		13	$ 987	573	2,279
Distributions to partners		3,800		3,800
Non-controlling interest distribution					$ 0
Cash	737	737		737		15,948
Accounts receivable						598
Accounts payable						759
Contract liabilities	212	212		212		1,480
Due to Primoris						7,428
Wilmington | Non Controlling Interest
Noncontrolling Interests
Distributions to partners		3,800		3,800
Carlsbad and Wilmington
Noncontrolling Interests
Cash	15,729	15,729		15,729		60,256
Accounts receivable	109	109		109		15,941
Contract assets	12,620	12,620		12,620
Accounts payable	2,673	2,673		2,673		13,111
Contract liabilities	$ 9,836	$ 9,836		$ 9,836		$ 44,223