Financial Information of Company's Operation by Segment (Detail) - USD ($) $ in Thousands	3 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Jun. 30, 2018
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
Revenues	$ 314,433	$ 261,503
Operating income	37,213	29,777
Interest expense	(5,584)	(3,645)
Other income (expense), net	713	767
Income taxes	(6,193)	(5,758)
Net earnings	26,149	21,141
Depreciation and amortization	22,170	18,816
Segment assets	1,880,643		$ 1,761,661
Expenditures for property, plant & equipment	34,918	37,426
Investments	75,289		$ 69,215
II-VI Laser Solutions
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
Revenues	106,175
II-VI Photonics
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
Revenues	135,156
II- VI Performance Products
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
Revenues	73,102
Operating Segments | II-VI Laser Solutions
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
Revenues	106,175	87,936
Inter-segment revenues	13,553	7,180
Operating income	12,310	2,655
Depreciation and amortization	10,847	8,224
Segment assets	751,801
Expenditures for property, plant & equipment	11,593	12,761
Operating Segments | II-VI Photonics
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
Revenues	135,156	115,940
Inter-segment revenues	2,896	2,863
Operating income	15,912	20,108
Depreciation and amortization	6,199	5,507
Segment assets	671,992
Expenditures for property, plant & equipment	12,051	9,782
Investments	13,373
Operating Segments | II- VI Performance Products
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
Revenues	73,102	57,627
Inter-segment revenues	5,662	827
Operating income	8,991	7,014
Depreciation and amortization	5,124	5,085
Segment assets	456,850
Expenditures for property, plant & equipment	11,274	14,883
Investments	61,916
Eliminations
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
Inter-segment revenues	$ (22,111)	$ (10,870)