Document and Entity Information Document - shares	9 Months Ended
	Sep. 30, 2017	Oct. 25, 2017
Entity Information [Line Items]
Entity Registrant Name	GRANITE CONSTRUCTION INC
Entity Central Index Key	0000861459
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Sep. 30, 2017
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	Q3
Amendment Flag	false
Entity Common Stock, Shares Outstanding		39,850,783