Dividends and Earnings Per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	0 Months Ended						3 Months Ended		9 Months Ended
	Oct. 15, 2013	Aug. 02, 2013	Jul. 15, 2013	May 03, 2013	Apr. 15, 2013	Mar. 05, 2013	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Dividends and Earnings Per Share
Cash dividend declared (in dollars per share)		$ 0.035		$ 0.035		$ 0.03
Total dividend paid	$ 1,805		$ 1,805		$ 1,547				$ 3,352	$ 4,611
Numerator:
Net income attributable to Primoris							$ 21,845	$ 17,516	$ 47,179	$ 39,735
Denominator:
Weighted average shares for computation of basic earnings per share							51,568	51,398	51,529	51,387
Dilutive effect of shares issued to independent directors							3	6	10	15
Dilutive effect of shares issued as part of Q3C acquisition									1
Dilutive effect of unvested restricted stock units							100		55
Weighted average shares for computation of diluted earnings per share							51,671	51,404	51,595	51,402
Earnings per share:
Basic earnings per share (in dollars per share)							$ 0.42	$ 0.34	$ 0.92	$ 0.77
Diluted earnings per share (in dollars per share)							$ 0.42	$ 0.34	$ 0.91	$ 0.77