CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	AOCI Including Portion Attributable to Noncontrolling Interest [Member]	Retained Earnings [Member]	Total Granite Shareholders' Equity [Member]	Noncontrolling Interests [Member]
Beginning Balance at Dec. 31, 2014	$ 817,106	$ 392	$ 134,605	$ (428)	$ 659,816	$ 794,385	$ 22,721
Beginning Balance (in shares) at Dec. 31, 2014		39,186,386
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	68,248	$ 0	0	0			7,763
Net Income Attributable to Parent	60,485				60,485	60,485
Other comprehensive income (loss)	(1,072)	0	0	(1,072)		(1,072)	0
Stock units vested	3	$ 3	0	0	0	3	0
Stock units vested (in shares)		317,524
Amortized restricted stock units	8,763	$ 0	8,763	0	0	8,763	0
Purchase of common stock	(3,856)	$ (1)	(3,855)	0	0	(3,856)	0
Purchase of common stock (in shares)		(114,969)
Cash dividends on common stock	(20,476)	$ 0	0	0	(20,476)	(20,476)	0
Transactions with noncontrolling interests, net	400	0	0	0	0	0	400
Stock options exercised and other	1,005	$ 0	1,399	0	(394)	1,005	0
Stock options exercised and other (in shares)		23,936
Ending Balance at Dec. 31, 2015	870,121	$ 394	140,912	(1,500)	699,431	839,237	30,884
Ending Balance (in shares) at Dec. 31, 2015		39,412,877
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	66,200	$ 0	0	0			9,078
Net Income Attributable to Parent	57,122				57,122	57,122
Other comprehensive income (loss)	1,129	0	0	1,129	0	1,129	0
Stock units vested	3	$ 3	0	0	0	3	0
Stock units vested (in shares)		308,619
Amortized restricted stock units	13,383	$ 0	13,383	0	0	13,383	0
Purchase of common stock	(5,227)	$ (1)	(5,226)	0	0	(5,227)	0
Purchase of common stock (in shares)		(116,355)
Cash dividends on common stock	(20,590)	$ 0	0	0	(20,590)	(20,590)	0
Transactions with noncontrolling interests, net	3,359	0	0	0	0	0	3,359
Stock options exercised and other	931	$ 0	1,268	0	(337)	931	0
Stock options exercised and other (in shares)		15,999
Ending Balance at Dec. 31, 2016	$ 922,591	$ 396	150,337	(371)	735,626	885,988	36,603
Ending Balance (in shares) at Dec. 31, 2016	39,621,140	39,621,140
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 75,801	$ 0	0				6,703
Net Income Attributable to Parent	69,098				69,098	69,098
Other comprehensive income (loss)	1,005	0	0	1,005	0	1,005	0
Stock units vested	4	$ 4	0		0	4	0
Stock units vested (in shares)		375,100
Amortized restricted stock units	15,764	$ 0	15,764		0	15,764	0
Purchase of common stock	(6,977)	$ (1)	(6,976)		0	(6,977)	0
Purchase of common stock (in shares)		(140,070)
Cash dividends on common stock	(20,720)	$ 0	0		(20,720)	(20,720)	0
Transactions with noncontrolling interests, net	4,391	0	0	0	0	0	4,391
Stock options exercised and other	946	$ 0	1,251	0	(305)	946	0
Stock options exercised and other (in shares)		15,144
Ending Balance at Dec. 31, 2017	$ 992,805	$ 399	$ 160,376	$ 634	$ 783,699	$ 945,108	$ 47,697
Ending Balance (in shares) at Dec. 31, 2017	39,871,314	39,871,314