Equity - Schedule of Stockholders Equity (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018		Jun. 30, 2017
Stockholders Equity Rollforward [Line Items]
Stockholders' equity, beginning balance				$ 992,805		$ 922,591
Net (loss) income		$ (6,081)	$ 16,272	(15,743)		(7,579)
Purchase of common stock				(6,165)	[1]	(6,568)	[2]
Dividends on common stock				(11,146)		(10,354)
Effect of adopting Topic 606				(15,202)
Issuance of common stock for Layne acquisition	[3]			321,123
Transactions with non-controlling interests				(6,400)
Other transactions with shareholders and employees	[4]			11,012		11,987
Stockholders' equity, ending balance		1,300,986	910,077	1,300,986		910,077
8.0 % Convertible Notes [Member]
Stockholders Equity Rollforward [Line Items]
Premium on convertible 8% notes	[5]	30,702		30,702
Granite Construction [Member]
Stockholders Equity Rollforward [Line Items]
Stockholders' equity, beginning balance				945,108		885,988
Net (loss) income				(19,808)		(9,657)
Purchase of common stock				(6,165)	[1]	(6,568)	[2]
Dividends on common stock				(11,146)		(10,354)
Effect of adopting Topic 606				(15,202)
Issuance of common stock for Layne acquisition	[3]			321,075
Transactions with non-controlling interests				0
Other transactions with shareholders and employees	[4]			11,012		11,987
Stockholders' equity, ending balance		1,255,576	871,396	1,255,576		871,396
Granite Construction [Member] | 8.0 % Convertible Notes [Member]
Stockholders Equity Rollforward [Line Items]
Premium on convertible 8% notes	[5]	30,702		30,702
Noncontrolling Interest [Member]
Stockholders Equity Rollforward [Line Items]
Stockholders' equity, beginning balance				47,697		36,603
Net (loss) income				4,065		2,078
Purchase of common stock				0	[1]	0	[2]
Dividends on common stock				0		0
Effect of adopting Topic 606				0
Issuance of common stock for Layne acquisition	[3]			48
Transactions with non-controlling interests				(6,400)
Other transactions with shareholders and employees	[4]			0		0
Stockholders' equity, ending balance		45,410	$ 38,681	45,410		$ 38,681
Noncontrolling Interest [Member] | 8.0 % Convertible Notes [Member]
Stockholders Equity Rollforward [Line Items]
Premium on convertible 8% notes	[5]	$ 0		$ 0

[1] Represents 104,000 shares purchased in connection with employee tax withholding for restricted stock units vested under our 2012 Equity Incentive Plan.

[2] Represents 133,000 shares purchased in connection with employee tax withholding for restricted stock units vested under our 2012 Equity Incentive Plan.

[3] Represents 5,624,000 shares issued in connection with the Layne acquisition wherein each share of Layne common stock was exchanged for 0.27 shares of Granite common stock. See Note 3 for further information.

[4] Amounts are comprised primarily of amortized restricted stock units.

[5] Represents premium associated with the conversion feature on the 8.0% Convertible Notes assumed from the acquisition of Layne. See Note 14 for further discussion.