Acquisitions (Details) - USD ($) $ / shares in Units, $ in Thousands			12 Months Ended
	Dec. 12, 2016	Feb. 01, 2016	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2015
Business Acquisition [Line Items]
Acquisition Related Adjustment for Final Working Capital Settlement				$ 88
Accrued working capital adjustment			$ 0	1,687	$ 0
Goodwill			$ 96,162	113,501	78,293	$ 71,518
Houston Interests, LLC [Member]
Business Acquisition [Line Items]
Net purchase price	$ 42,506
Cash paid for equity interest	46,000
Acquisition Related Adjustment for Final Working Capital Settlement	6,837
Cash consideration paid	42,506
Accounts receivable	10,273
Costs and estimated earnings in excess of billings on uncompleted contracts	746
Other current assets	454
Current assets	21,804
Property, plant and equipment	942
Tax deductible goodwill	35,146
Other intangible assets	10,220
Total assets acquired	68,112
Accounts payable	962
Billings on uncompleted contracts in excess of costs and estimated earnings	11,648
Other accrued expenses	2,475
Current liabilities	15,085
Other liabilities	190
Net assets acquired	52,837
Cash acquired	$ 10,331
Pro Forma Information:
Revenues				1,233,372	1,427,313
Net income attributable to Matrix Service Company				$ 7,326	$ 32,352
Basic earnings per common share (in dollars per share)				$ 0.28	$ 1.22
Diluted earnings per common share (in dollars per share)				$ 0.27	$ 1.19
Pro forma acquisition costs				$ 3,300
Pro forma acquisition costs, amortized over time				800	$ 900
Pro forma interest expense				700	1,400
Pro forma depreciation and amortization expense				1,400	1,800
Pro forma income tax expense				$ 2,000	$ 2,200
Baillie Tank Equipment, Ltd. [Member]
Business Acquisition [Line Items]
Net purchase price		$ 13,049
Current assets		5,574
Property, plant and equipment		4,347
Goodwill		7,030
Other intangible assets		720
Other assets		233
Total assets acquired		17,904
Current liabilities		1,669
Deferred income taxes		329
Long-term debt		1,858
Other liabilities		407
Net assets acquired		13,641
Cash acquired		$ 592