BASIS OF PRESENTATION, CONSOLIDATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details) - USD ($)	3 Months Ended					9 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Jun. 30, 2017	Mar. 31, 2019	Mar. 31, 2018
Item Affected [Line Items]
Allowance for doubtful accounts receivable				$ 3,200,000			$ 3,300,000
Inventory allowance				24,600,000			26,000,000
Inventory write-down					$ 1,192,000
Short-term portion of contract acquisition and pre-operating costs				10,100,000			10,800,000
Amortization of other deferred charges				2,700,000	2,900,000
Goodwill				19,175,000			19,907,000
Accumulated goodwill impairment				50,861,000			50,861,000
Long-term portion of contract acquisition and pre-operating costs				45,200,000			50,600,000
Deferred OEM cost recovery				$ 5,378,000			8,082,000
Property, Plant and Equipment, Salvage Value, Percentage				50.00%
Other accrued liabilities				$ 51,325,000			65,978,000
Accounting Standards Update 2016-16 [Member] | Retained Earnings
Item Affected [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets				(1,700,000)
Accounting Standards Update 2017-07 [Member]
Item Affected [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Operating Results					$ 100,000
OEM Cost recoveries
Item Affected [Line Items]
Original Equipment Manufacturer, Recoveries Sought							136,000,000
Original Equipment Manufacturer, Amount Received				11,000,000			125,000,000
Accumulated Depreciation, Period Increase (Decrease)							(94,500,000)
Deferred OEM cost recovery				10,400,000			13,900,000
OEM Cost recoveries | Depreciation Expense [Member]
Item Affected [Line Items]
Offset Amount, Expense, Remainder of Fiscal Year				6,400,000
Offset Amount, Expense, Rolling Year Two				8,400,000
Offset Amount, Expense, Rolling Year Three				5,600,000
Offset Amount, Expense, Rolling Year Four And Thereafter				21,300,000
OEM Cost recoveries | Rent Expense
Item Affected [Line Items]
Offset Amount, Expense				3,500,000			16,600,000
Offset Amount, Expense, Remainder of Fiscal Year				4,400,000
Offset Amount, Expense, Rolling Year Two				4,000,000
Offset Amount, Expense, Rolling Year Three				2,000,000
OEM Cost recoveries | Revenue
Item Affected [Line Items]
Former Gain Contingency, Recognized in Current Period				7,600,000
OEM Cost recoveries | Direct cost
Item Affected [Line Items]
Former Gain Contingency, Recognized in Current Period				1,100,000
OEM Cost recoveries | Direct cost | Scenario, Forecast [Member]
Item Affected [Line Items]
Effect on Future Earnings, Offset Amount	$ (300,000)	$ (1,000,000)	$ (1,000,000)			$ (2,300,000)
Affiliated entity
Item Affected [Line Items]
Allowance for doubtful accounts receivable				$ 0			$ 0