Business Combinations - Acquired Intangible Assets (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Pro forma results
Pro forma tax rate used in calculating taxes on income from continuing operations (as a percent)	40.00%		40.00%
Revenues	$ 456,811	$ 484,620	$ 887,615	$ 881,473
Income before provision for income taxes	8,620	6,092	13,440	7,483
Net income attributable to Primoris	$ 5,056	$ 3,674	$ 7,793	$ 4,532
Weighted average common shares outstanding:
Basic (in shares)	51,772	51,666	51,749	51,619
Diluted (in shares)	52,022	51,815	51,950	51,770
Earnings per share:
Basic (in dollars per share)	$ 0.10	$ 0.07	$ 0.15	$ 0.09
Diluted (in dollars per share)	$ 0.10	$ 0.07	$ 0.15	$ 0.09