Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current assets
Cash and cash equivalents	$ 262,273	$ 184,673	$ 144,958	$ 200,263	$ 272,804	$ 230,259	$ 195,515	$ 193,581	$ 233,711
Short-term marketable securities	27,799	37,918	41,037	36,049	30,002	35,010	20,014	39,961
Receivables, net	547,417	712,972	564,543	380,985	484,753	623,123	497,771	335,315
Contract assets	211,441	206,407	224,389	213,023	184,247	205,958	252,609	165,770
Inventories	88,885	95,442	101,686	96,862	88,623	90,789	96,024	71,295
Equity in construction joint ventures	193,110	203,954	220,247	219,908	231,365	234,716	215,093	200,310
Other current assets	46,016	51,925	80,560	62,755	48,710	32,185	47,293	46,122
Total current assets	1,376,941	1,493,291	1,377,420	1,209,845	1,340,504	1,515,028	1,324,319	1,052,354
Property and equipment, net	542,297	542,796	558,378	552,504	549,688	560,618	598,871	409,708
Long-term marketable securities	5,000	10,000	20,000	30,000	36,098	46,093	61,191	67,305
Investments in affiliates	84,176	84,914	82,109	81,034	84,354	84,840	91,695	38,682
Goodwill	264,279	264,112	264,107	259,695	259,471	244,696	254,058	53,799
Right of use assets	72,534	70,472	73,439	71,480	0	0	0	0
Deferred income taxes, net	50,158	30,637	28,249	30,488	30,142	25,888	44,892	23,200
Other noncurrent assets	106,703	116,438	120,915	123,557	126,893	143,910	154,009	74,382
Total assets	2,502,088	2,612,660	2,524,617	2,358,603	2,427,150	2,621,073	2,529,035	1,719,430
Current liabilities
Current maturities of long-term debt	8,244	8,263	48,397	47,281	47,286	116,796	207,982	47,298
Accounts payable	400,775	399,743	302,651	216,150	256,757	316,917	303,885	227,091
Contract liabilities	95,737	109,299	128,443	104,260	109,011	118,986	92,657	70,962
Accrued expenses and other current liabilities	337,300	359,221	360,231	308,086	324,383	320,713	326,781	268,766
Total current liabilities	842,056	876,526	839,722	675,777	737,437	873,412	931,305	614,117
Long-term debt	356,108	394,841	366,896	333,290	335,119	316,926	280,710	176,011
Long-term lease liabilities	58,618	56,740	60,868	60,237	0	0	0	0
Deferred income taxes, net	3,754	4,652	4,680	4,913	4,160	5,589	5,699	0
Other long-term liabilities	63,136	58,433	58,268	59,867	61,080	67,429	71,180	40,104
Commitments and contingencies
Equity
Preferred stock, $0.01 par value, authorized 3,000,000 shares, none outstanding	0	0	0	0	0	0	0	0
Common stock, $0.01 par value, authorized 150,000,000 shares; issued and outstanding: 45,503,805 shares as of December 31, 2019 and 46,665,889 shares as of December 31, 2018	456	468	468	468	467	469	457	400
Additional paid-in capital	549,307	567,033	568,264	566,497	564,559	572,046	516,680	162,038
Accumulated other comprehensive loss	(2,645)	(3,282)	(2,187)	(1,081)	(749)	1,841	1,022	1,197
Retained earnings	594,353	619,690	579,920	610,302	679,453	738,254	676,572	676,705
Total Granite Construction Incorporated shareholders’ equity	1,141,471	1,183,909	1,146,465	1,176,186	1,243,730	1,312,610	1,194,731	840,340
Non-controlling interests	36,945	37,559	47,718	48,333	45,624	45,107	45,410	48,858
Total equity	1,178,416	1,221,468	1,194,183	1,224,519	1,289,354	1,357,717	1,240,141	889,198	$ 921,147	$ 884,315
Total liabilities and equity	$ 2,502,088	$ 2,612,660	$ 2,524,617	$ 2,358,603	$ 2,427,150	$ 2,621,073	$ 2,529,035	$ 1,719,430