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		(15,743)	$ 0	0	0	(19,808)	(19,808)	4,065
Other comprehensive income (loss)		390	0	0	390	0	390	0
Purchases of common stock	[1]	(6,165)	$ (1)	(6,164)	0	0	(6,165)	0
Purchases of common stock (in shares)	[1]		(104,432)
Restricted stock units (“RSUs”) vested		3	$ 3	0	0	0	3	0
Restricted stock units (“RSUs”) vested (in shares)			290,321
Dividends on common stock		(11,146)	$ 0	0	0	(11,146)	(11,146)	0
Effect of adopting Accounting Standards Update | ASU 2014-09 [Member]		(15,201)	0	0	0	(15,201)	(15,201)	0
Issuance of common stock for Layne acquisition		321,123	$ 56	321,019	0	0	321,075	48
Issuance of common stock for Layne acquisition (in shares)			5,624,021
Premium on 8.0% Convertible Notes		30,702	$ 0	30,702	0	0	30,702	0
Transactions with non-controlling interests		(6,400)	0	0	0	0	0	(6,400)
Employee Stock Purchase Plan ("ESPP"), amortized RSUs and other		10,618	$ 0	10,747	(2)	(127)	10,618	0
Employee Stock Purchase Plan (ESPP"), amortized RSUs and other (in shares)			7,358
Ending Balance at Jun. 30, 2018		$ 1,300,986	$ 457	516,680	1,022	737,417	1,255,576	45,410
Ending Balance (in shares) at Jun. 30, 2018		45,688,582	45,688,582
Beginning Balance at Mar. 31, 2018		$ 964,894	$ 400	162,038	1,197	751,801	915,436	49,458
Beginning Balance (in shares) at Mar. 31, 2018			40,047,187
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income		(6,081)	$ 0	0	0	(8,385)	(8,385)	2,304
Other comprehensive income (loss)		(173)	0	0	(173)	0	(173)	0
Purchases of common stock	[1]	(46)	$ 0	(46)	0	0	(46)	0
Purchases of common stock (in shares)	[1]		(834)
Restricted stock units (“RSUs”) vested		1	$ 1	0	0	0	1	0
Restricted stock units (“RSUs”) vested (in shares)			9,712
Dividends on common stock		(5,940)	$ 0	0	0	(5,940)	(5,940)	0
Issuance of common stock for Layne acquisition		321,123	$ 56	321,019	0	0	321,075	48
Issuance of common stock for Layne acquisition (in shares)			5,624,021
Premium on 8.0% Convertible Notes		30,702	$ 0	30,702	0	0	30,702	0
Transactions with non-controlling interests		(6,400)	0	0	0	0	0	(6,400)
Employee Stock Purchase Plan ("ESPP"), amortized RSUs and other		2,906	$ 0	2,967	(2)	(59)	2,906	0
Employee Stock Purchase Plan (ESPP"), amortized RSUs and other (in shares)			8,496
Ending Balance at Jun. 30, 2018		$ 1,300,986	$ 457	516,680	1,022	737,417	1,255,576	45,410
Ending Balance (in shares) at Jun. 30, 2018		45,688,582	45,688,582
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		$ (125,042)	$ 0	0	0	(132,410)	(132,410)	7,368
Other comprehensive income (loss)		(2,699)	0	0	(2,699)	0	(2,699)	0
Purchases of common stock	[1]	(3,948)	$ (1)	(3,947)	0	0	(3,948)	0
Purchases of common stock (in shares)	[1]		(88,091)
Restricted stock units (“RSUs”) vested		2	$ 2	0	0	0	2	0
Restricted stock units (“RSUs”) vested (in shares)			251,393
Dividends on common stock		(12,175)	$ 0	0	0	(12,175)	(12,175)	0
Effect of adopting Accounting Standards Update | ASU 2016-02 [Member]		(539)	0	0	0	(539)	(539)	0
Transactions with non-controlling interests		(3,209)	0	0	0	0	0	(3,209)
Employee Stock Purchase Plan ("ESPP"), amortized RSUs and other		7,544	$ 0	7,652	0	(108)	7,544	0
Employee Stock Purchase Plan (ESPP"), amortized RSUs and other (in shares)			9,008
Ending Balance at Jun. 30, 2019		$ 1,257,568	$ 468	568,264	(3,448)	642,124	1,207,408	50,160
Ending Balance (in shares) at Jun. 30, 2019		46,838,199	46,838,199
Beginning Balance at Mar. 31, 2019		$ 1,361,933	$ 468	566,497	(626)	746,100	1,312,439	49,494
Beginning Balance (in shares) at Mar. 31, 2019			46,812,366
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income		(93,961)	$ 0	0	0	(97,836)	(97,836)	3,875
Other comprehensive income (loss)		(2,822)	0	0	(2,822)	0	(2,822)	0
Purchases of common stock	[1]	(81)	$ 0	(81)	0	0	(81)	0
Purchases of common stock (in shares)	[1]		(1,987)
Restricted stock units (“RSUs”) vested		0	$ 0	0	0	0	0	0
Restricted stock units (“RSUs”) vested (in shares)			17,443
Dividends on common stock		(6,089)	$ 0	0	0	(6,089)	(6,089)	0
Transactions with non-controlling interests		(3,209)	0	0	0	0	0	(3,209)
Employee Stock Purchase Plan ("ESPP"), amortized RSUs and other		1,797	$ 0	1,848	0	(51)	1,797	0
Employee Stock Purchase Plan (ESPP"), amortized RSUs and other (in shares)			10,377
Ending Balance at Jun. 30, 2019		$ 1,257,568	$ 468	$ 568,264	$ (3,448)	$ 642,124	$ 1,207,408	$ 50,160
Ending Balance (in shares) at Jun. 30, 2019		46,838,199	46,838,199

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