CONDENSED CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) $ in Thousands		Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Other Comprehensive (Loss) Income [Member]	Retained Earnings [Member]	Total Granite Shareholders' Equity [Member]	Non-controlling Interests [Member]
Beginning Balance at Dec. 31, 2017		$ 992,805	$ 399	$ 160,376	$ 634	$ 783,699	$ 945,108	$ 47,697
Beginning Balance (in shares) at Dec. 31, 2017			39,871,314
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income		(9,662)				(11,423)	(11,423)	1,761
Other comprehensive income		563			563		563
Purchases of common stock	[1]	(6,119)	$ (1)	(6,118)			(6,119)
Purchases of common stock (in shares)	[1]		(103,598)
Restricted stock units (“RSUs”) vested		2	$ 2				2
Restricted stock units (“RSUs”) vested (in shares)			280,609
Dividends on common stock		(5,206)				(5,206)	(5,206)
Effect of adopting Accounting Standards Update | Topic 606 [Member]		(15,201)				(15,201)	(15,201)
Other transactions with shareholders and employees	[2]	7,712		7,780		(68)	7,712
Other transactions with shareholders and employees (in shares)	[2]		(1,138)
Ending Balance at Mar. 31, 2018		$ 964,894	$ 400	162,038	1,197	751,801	915,436	49,458
Ending Balance (in shares) at Mar. 31, 2018		40,047,187	40,047,187
Beginning Balance at Dec. 31, 2018		$ 1,397,634	$ 467	564,559	(749)	787,356	1,351,633	46,001
Beginning Balance (in shares) at Dec. 31, 2018		46,665,889	46,665,889
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income		$ (31,081)				(34,574)	(34,574)	3,493
Other comprehensive income		123			123		123
Purchases of common stock	[1]	(3,867)	$ (1)	(3,866)			(3,867)
Purchases of common stock (in shares)	[1]		(86,104)
Restricted stock units (“RSUs”) vested		2	$ 2				2
Restricted stock units (“RSUs”) vested (in shares)			233,950
Dividends on common stock		(6,086)				(6,086)	(6,086)
Effect of adopting Accounting Standards Update | Topic 842 [Member]		(539)				(539)	(539)
Other transactions with shareholders and employees	[2]	5,747		5,804		(57)	5,747
Other transactions with shareholders and employees (in shares)	[2]		(1,369)
Ending Balance at Mar. 31, 2019		$ 1,361,933	$ 468	$ 566,497	$ (626)	$ 746,100	$ 1,312,439	$ 49,494
Ending Balance (in shares) at Mar. 31, 2019		46,812,366	46,812,366

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

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