Condensed Consolidated Statements of Operations (Unaudited) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Revenue
Total revenue	$ 635,927	$ 581,813
Cost of revenue
Total cost of revenue	612,128	580,675
Gross profit	23,799	1,138
Selling, general and administrative expenses	78,381	80,155
Acquisition and integration expenses	0	1,848
Non-cash impairment charges (See Note 4)	24,413	0
Gain on sales of property and equipment	(623)	(1,900)
Operating loss	(78,372)	(78,965)
Other (income) expense
Interest income	(1,291)	(2,816)
Interest expense	4,994	4,014
Equity in income of affiliates, net	(46)	(1,290)
Other expense (income), net	5,219	(1,762)
Total other expense (income)	8,876	(1,854)
Loss before benefit from income taxes	(87,248)	(77,111)
Benefit from income taxes	(14,710)	(17,350)
Net loss	(72,538)	(59,761)	$ (59,761)
Amount attributable to non-controlling interests	7,168	(2,709)
Net loss attributable to Granite Construction Incorporated	$ (65,370)	$ (62,470)
Net loss per share attributable to common shareholders (See Note 16)
Basic (in dollars per share)	$ (1.44)	$ (1.34)
Diluted (in dollars per share)	$ (1.44)	$ (1.34)
Weighted average shares of common stock
Basic (in shares)	45,520	46,699
Diluted (in shares)	45,520	46,699
Transportation [Member]
Revenue
Total revenue	$ 350,901	$ 301,964
Cost of revenue
Total cost of revenue	325,532	318,312
Water [Member]
Revenue
Total revenue	101,657	99,082
Cost of revenue
Total cost of revenue	92,310	91,136
Specialty [Member]
Revenue
Total revenue	133,039	139,124
Cost of revenue
Total cost of revenue	143,758	125,826
Materials [Member]
Revenue
Total revenue	50,330	41,643
Cost of revenue
Total cost of revenue	$ 50,528	$ 45,401