Financial Information of Company's Operation by Segment (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018	Jun. 30, 2018
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
Revenues	$ 342,496	$ 294,746	$ 999,768	$ 837,719
Operating income (expense)	31,130	34,479	107,949	96,739
Interest expense	(5,647)	(5,014)	(16,811)	(13,303)
Other income (expense), net	1,532	1,755	2,946	4,551
Income taxes	(2,377)	(1,122)	(14,595)	(27,152)
Net earnings	24,638	30,098	79,489	60,835
Depreciation and amortization	23,161	19,924	67,627	58,149
Segment assets	1,941,977		1,941,977		$ 1,761,661
Expenditures for property, plant & equipment	34,783	38,614	108,170	115,437
Investments	76,452		76,452		$ 69,215
II-VI Laser Solutions
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
Revenues	97,474		309,226
II-VI Photonics
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
Revenues	166,473		461,323
II-VI Performance Products
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
Revenues	78,549		229,219
Operating Segments | II-VI Laser Solutions
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
Revenues	97,474	104,537	309,226	297,506
Inter-segment revenues	15,301	8,268	42,486	22,335
Operating income (expense)	5,937	11,602	30,469	23,695
Depreciation and amortization	11,189	10,112	32,629	27,165
Segment assets	721,234		721,234
Expenditures for property, plant & equipment	17,566	16,542	44,460	52,724
Operating Segments | II-VI Photonics
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
Revenues	166,473	122,037	461,323	353,281
Inter-segment revenues	3,115	(175)	8,451	8,185
Operating income (expense)	20,723	14,024	59,722	49,687
Depreciation and amortization	6,795	5,843	19,456	17,019
Segment assets	685,141		685,141
Expenditures for property, plant & equipment	11,177	14,754	34,451	32,429
Operating Segments | II-VI Performance Products
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
Revenues	78,549	68,172	229,219	186,932
Inter-segment revenues	5,392	6,870	17,113	19,180
Operating income (expense)	8,377	8,853	28,768	23,357
Depreciation and amortization	5,177	3,969	15,542	13,965
Segment assets	535,602		535,602
Expenditures for property, plant & equipment	6,040	7,319	29,259	30,284
Investments	76,452		76,452
Eliminations & Other
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
Inter-segment revenues	(23,808)	$ (14,963)	(68,050)	$ (49,700)
Operating income (expense)	$ (3,907)		$ (11,010)