Note 7 - Unearned Revenue - Schedule of Unearned Revenue (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019
Unearned Revenue	$ 3,600,028	$ 3,717,228	$ 2,997,499
Water and Mineral Services [Member]
Unearned Revenue	143,539	152,141	193,915
California 1[Member]
Unearned Revenue	674,113	645,610	478,494
Federal [Member]
Unearned Revenue	150,678	168,743	136,448
Heavy Civil [Member]
Unearned Revenue	1,603,014	1,770,742	1,440,736
Midwest [Member]
Unearned Revenue	349,483	366,721	312,608
Northwest [Member]
Unearned Revenue	679,201	613,271	435,298
Transportation [Member]
Unearned Revenue	2,691,091	2,798,056	2,316,675
Transportation [Member] | Water and Mineral Services [Member]
Unearned Revenue	0	0	0
Transportation [Member] | California 1[Member]
Unearned Revenue	527,971	525,641	402,112
Transportation [Member] | Federal [Member]
Unearned Revenue	18,152	14,139	126
Transportation [Member] | Heavy Civil [Member]
Unearned Revenue	1,321,443	1,480,367	1,423,909
Transportation [Member] | Midwest [Member]
Unearned Revenue	208,872	230,889	128,867
Transportation [Member] | Northwest [Member]
Unearned Revenue	614,653	547,020	361,661
Water [Member]
Unearned Revenue	241,161	224,875	221,675
Water [Member] | Water and Mineral Services [Member]
Unearned Revenue	143,539	152,141	193,915
Water [Member] | California 1[Member]
Unearned Revenue	52,136	19,950	7,314
Water [Member] | Federal [Member]
Unearned Revenue	957	1,041	1,717
Water [Member] | Heavy Civil [Member]
Unearned Revenue	41,511	47,046	16,827
Water [Member] | Midwest [Member]
Unearned Revenue	150	152	143
Water [Member] | Northwest [Member]
Unearned Revenue	2,868	4,545	1,759
Specialty [Member]
Unearned Revenue	667,776	694,297	459,149
Specialty [Member] | Water and Mineral Services [Member]
Unearned Revenue	0	0	0
Specialty [Member] | California 1[Member]
Unearned Revenue	94,006	100,019	69,068
Specialty [Member] | Federal [Member]
Unearned Revenue	131,569	153,563	134,605
Specialty [Member] | Heavy Civil [Member]
Unearned Revenue	240,060	243,329	0
Specialty [Member] | Midwest [Member]
Unearned Revenue	140,461	135,680	183,598
Specialty [Member] | Northwest [Member]
Unearned Revenue	$ 61,680	$ 61,706	$ 71,878