Stockholders' Equity (Details) $ / shares in Units, $ in Thousands	1 Months Ended							3 Months Ended	12 Months Ended			56 Months Ended
	Aug. 31, 2017 shares	Feb. 28, 2017 USD ($) shares	Dec. 31, 2016 USD ($) $ / shares shares	Aug. 31, 2016 USD ($) shares	Feb. 29, 2016 shares	Aug. 31, 2015 shares	Mar. 31, 2015 shares	Mar. 31, 2017 USD ($) $ / shares shares	Dec. 31, 2017 USD ($) item $ / shares shares	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) shares	Dec. 31, 2017 $ / shares shares
Common Stock
Common stock, shares authorized			90,000,000						90,000,000	90,000,000		90,000,000
Common stock, par value (in dollars per share) | $ / shares			$ 0.0001						$ 0.0001	$ 0.0001		$ 0.0001
Common stock, shares issued			51,576,442						51,448,753	51,576,442		51,448,753
Common stock, shares outstanding			51,576,442						51,448,753	51,576,442		51,448,753
Number of holders of common stock | item									365
Shares of common stock issued as a part of quarterly compensation of non-employee members of the Board of Directors	11,448	11,784		11,745	10,450	9,748	8,168
Period of restriction on trade for shares issued to non-employee members of the board of directors under the Primoris Long-term Retention Plan									1 year
Aggregate purchase price up to which shares can be acquired under share repurchase program | $		$ 5,000		$ 5,000
Number of shares purchased and cancelled under the share repurchase program			207,800					216,350			0
Amount paid for shares purchased and cancelled under share repurchase program | $			$ 5,000					$ 5,000
Amount paid for shares purchased and cancelled under share repurchase program (per share) | $ / shares			$ 24.02					$ 23.10
Preferred Stock
Preferred stock, authorized (in shares)			1,000,000						1,000,000	1,000,000		1,000,000
Par value of preferred stock (in dollars per share) | $ / shares			$ 0.0001						$ 0.0001	$ 0.0001		$ 0.0001
Preferred stock, shares outstanding			0						0	0	0	0
Warrants
Warrants outstanding (in shares)			0						0	0	0	0
Restricted Stock Units
Common Stock
Granted, Units												259,065
LTR Plan
Common Stock
Shares of common stock issued under the long-term incentive plan									65,429	85,907	96,828
Amount received in exchange for shares of common stock under a long term incentive plan | $									$ 1,100	$ 1,400	$ 1,600
Trading restriction									6 months
Percentage of average market closing prices used in determining number of common stock that could be purchased by participants									75.00%	75.00%	75.00%
Equity Plan
Common Stock
Shares of common stock reserved for issuance upon exercise of all future stock option grants, SARS and grants of restricted shares under the 2013 Equity Plan									1,853,494			1,853,494
Equity Plan | Restricted Stock Units
Common Stock
Granted, Units									10,000	100,553	0	259,065