Note 6 - Unearned Revenue - Schedule of Unearned Revenue (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Jun. 30, 2019	Sep. 30, 2018
Unearned Revenue	$ 3,593,201	$ 3,692,312	$ 3,063,425
Water and Mineral Services [Member]
Unearned Revenue	159,874	224,720	211,531
California 1[Member]
Unearned Revenue	651,694	724,175	360,822
Federal [Member]
Unearned Revenue	193,566	147,946	145,506
Heavy Civil [Member]
Unearned Revenue	1,889,522	1,763,965	1,705,551
Midwest [Member]
Unearned Revenue	345,616	363,237	326,739
Northwest [Member]
Unearned Revenue	352,929	468,269	313,276
Transportation [Member]
Unearned Revenue	2,628,575	2,921,437	2,311,712
Transportation [Member] | Water and Mineral Services [Member]
Unearned Revenue	0	0	0
Transportation [Member] | California 1[Member]
Unearned Revenue	535,139	590,641	299,242
Transportation [Member] | Federal [Member]
Unearned Revenue	14,699	80	23
Transportation [Member] | Heavy Civil [Member]
Unearned Revenue	1,595,092	1,751,819	1,678,637
Transportation [Member] | Midwest [Member]
Unearned Revenue	207,555	204,749	91,144
Transportation [Member] | Northwest [Member]
Unearned Revenue	276,090	374,148	242,666
Water [Member]
Unearned Revenue	231,551	253,418	250,157
Water [Member] | Water and Mineral Services [Member]
Unearned Revenue	159,874	224,720	211,531
Water [Member] | California 1[Member]
Unearned Revenue	19,594	14,382	11,297
Water [Member] | Federal [Member]
Unearned Revenue	1,181	1,350	0
Water [Member] | Heavy Civil [Member]
Unearned Revenue	48,952	12,146	26,914
Water [Member] | Midwest [Member]
Unearned Revenue	70	110	405
Water [Member] | Northwest [Member]
Unearned Revenue	1,880	710	10
Specialty [Member]
Unearned Revenue	733,075	517,457	501,556
Specialty [Member] | Water and Mineral Services [Member]
Unearned Revenue	0	0	0
Specialty [Member] | California 1[Member]
Unearned Revenue	96,961	119,152	50,283
Specialty [Member] | Federal [Member]
Unearned Revenue	177,686	146,516	145,483
Specialty [Member] | Heavy Civil [Member]
Unearned Revenue	245,478	0	0
Specialty [Member] | Midwest [Member]
Unearned Revenue	137,991	158,378	235,190
Specialty [Member] | Northwest [Member]
Unearned Revenue	$ 74,959	$ 93,411	$ 70,600