SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Foreign Currency Translation and Transactions, Earnings per Share, Warranty Provision & Subsequent Events (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	1 Months Ended	12 Months Ended
Jul. 31, 2018	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2016
Foreign Currency Translation
Transaction gain (loss)		$ (1,300)	$ 2,000	$ (800)
Earnings (loss) per share:
Stock option and stock awards excluded from computation due to antidilutive effect (in shares)		1,300	100	100
Computation of basic and diluted earnings per share
Net income (loss) available to common stockholders		$ (29,127)	$ 21,076	$ 26,157
Weighted average shares outstanding-basic		18,592	18,894	19,427
Dilutive effect of equity awards			795	649
Weighted average shares outstanding-diluted		18,592	19,689	20,076
Basic earnings (loss) per share		$ (1.57)	$ 1.12	$ 1.35
Diluted earnings (loss) per share		$ (1.57)	$ 1.07	$ 1.30
Changes in warranty provision
Warranty provision at beginning of period	$ 21,819	$ 15,178	$ 15,948	$ 12,738
Warranty claims provided for/assumed in acquisition		14,156	5,793	12,296
Settlements made		(7,515)	(6,563)	(9,086)
Warranty provision at end of period		21,819	$ 15,178	$ 15,948
Subsequent Events
Maximum earnout consideration		$ 29,900
Optoelectronics solutions business \| Subsequent Event
Subsequent Events
Consideration paid	17,500
Maximum earnout consideration	$ 1,000

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Foreign Currency Translation and Transactions, Earnings per Share, Warranty Provision & Subsequent Events (Details) - USD ($)
$ / shares in Units, shares in Thousands, $ in Thousands

1 Months Ended

12 Months Ended

Jul. 31, 2018

Jun. 30, 2018

Jun. 30, 2017

Jun. 30, 2016

Foreign Currency Translation

Transaction gain (loss)

$ (1,300)

$ 2,000

$ (800)

Earnings (loss) per share:

Stock option and stock awards excluded from computation due to antidilutive effect (in shares)

1,300

100

Computation of basic and diluted earnings per share

Net income (loss) available to common stockholders

$ (29,127)

$ 21,076

$ 26,157

Weighted average shares outstanding-basic

18,592

18,894

19,427

Dilutive effect of equity awards

795

649

Weighted average shares outstanding-diluted

18,592

19,689

20,076

Basic earnings (loss) per share

$ (1.57)

$ 1.12

$ 1.35

Diluted earnings (loss) per share

$ (1.57)

$ 1.07

$ 1.30

Changes in warranty provision

Warranty provision at beginning of period

$ 21,819

$ 15,178

$ 15,948

$ 12,738

Warranty claims provided for/assumed in acquisition

14,156

5,793

12,296

Settlements made

(7,515)

(6,563)

(9,086)

Warranty provision at end of period

21,819

$ 15,178

$ 15,948

Subsequent Events

Maximum earnout consideration

$ 29,900

Optoelectronics solutions business | Subsequent Event

Subsequent Events

Consideration paid

17,500

Maximum earnout consideration

$ 1,000

- Definition

Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.