Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly Financial Data [Abstract]
Revenue, Net	$ 892,325	$ 1,055,591	$ 807,119	$ 563,379	$ 801,274	$ 957,126	$ 762,913	$ 468,400	$ 3,318,414	$ 2,989,713	$ 2,514,617
Gross profit	$ 108,049	$ 144,491	$ 80,369	$ 56,283	$ 100,707	$ 114,530	$ 74,570	$ 25,126	389,192	314,933	301,370
Gross profit as a percent of revenue	12.10%	13.70%	10.00%	10.00%	12.60%	12.00%	9.80%	5.40%
Net income (loss)	$ 10,387	$ 59,097	$ (6,081)	$ (9,662)	$ 35,325	$ 48,055	$ 16,272	$ (23,851)	53,741	75,801	66,200
Net income (loss) as a percent of revenue	1.20%	5.60%	(0.80%)	(1.70%)	4.40%	5.00%	2.10%	(5.10%)
Net income (loss) attributable to Granite	$ 6,546	$ 55,672	$ (8,385)	$ (11,423)	$ 32,773	$ 45,982	$ 14,133	$ (23,790)	$ 42,410	$ 69,098	$ 57,122
Net income (loss) attributable to Granite as a percent of revenue	0.70%	5.30%	(1.00%)	(2.00%)	4.10%	4.80%	1.90%	(5.10%)
Net income (loss) per share attributable to common shareholders:
Basic	$ 0.14	$ 1.20	$ (0.20)	$ (0.29)	$ 0.82	$ 1.15	$ 0.35	$ (0.60)	$ 0.97	$ 1.74	$ 1.44
Diluted	$ 0.14	$ 1.17	$ (0.20)	$ (0.29)	$ 0.81	$ 1.14	$ 0.35	$ (0.60)	$ 0.96	$ 1.71	$ 1.42