Financial Information of Company's Operation by Segment (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2015
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
Revenues	$ 273,717	$ 244,987	$ 231,822	$ 221,520	$ 241,470	$ 205,105	$ 191,434	$ 189,207	$ 972,046	$ 827,216	$ 741,961
Operating income									115,541	91,813	76,799
Interest expense	(2,262)	(1,936)	(1,365)	(1,246)	(1,066)	(769)	(597)	(649)	(6,809)	(3,081)	(3,863)
Other income, net	445	2,164	6,045	1,402	429	(1,257)	994	1,057	10,056	1,223	6,176
Income taxes	(1,211)	(6,837)	(7,913)	(7,553)	(13,934)	(2,426)	(3,187)	(4,922)	(23,514)	(24,469)	(13,137)
Net earnings	32,647	$ 22,430	$ 23,903	$ 16,294	14,343	$ 14,938	$ 18,991	$ 17,214	95,274	65,486	65,975
Depreciation and amortization									63,637	56,663	53,083
Expenditures for property, plant & equipment									142,945	58,170	52,313
Segment assets	1,477,297				1,211,981				1,477,297	1,211,981
Equity investment	11,727				11,354				11,727	11,354
Goodwill	250,342				233,755				250,342	233,755	195,894
Eliminations
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
Inter-segment revenues									(58,217)	(43,645)	(43,556)
II-VI Laser Solutions
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
Goodwill	84,180				84,105				84,180	84,105	43,578
II-VI Laser Solutions | Operating Segments
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
Revenues									339,341	303,002	287,881
Inter-segment revenues									33,792	24,290	21,021
Operating income									30,931	36,184	55,039
Depreciation and amortization									24,958	17,222	14,127
Expenditures for property, plant & equipment									82,760	25,620	27,349
Segment assets	589,239				469,754				589,239	469,754
Goodwill	84,180				84,105				84,180	84,105
II-VI Photonics
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
Goodwill	113,272				96,760				113,272	96,760	99,426
II-VI Photonics | Operating Segments
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
Revenues									418,515	325,879	260,825
Inter-segment revenues									14,236	12,081	13,210
Operating income									62,975	37,849	7,208
Depreciation and amortization									21,442	19,855	21,073
Expenditures for property, plant & equipment									27,397	21,096	11,324
Segment assets	578,315				467,486				578,315	467,486
Goodwill	113,272				96,760				113,272	96,760
II- VI Performance Products
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
Goodwill	52,890				52,890				52,890	52,890	52,890
II- VI Performance Products | Operating Segments
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
Revenues									214,190	198,335	193,255
Inter-segment revenues									10,189	7,274	9,325
Operating income									21,635	17,780	14,552
Depreciation and amortization									17,237	19,586	17,883
Expenditures for property, plant & equipment									32,788	11,454	$ 13,640
Segment assets	309,743				274,741				309,743	274,741
Equity investment	11,727				11,354				11,727	11,354
Goodwill	$ 52,890				$ 52,890				$ 52,890	$ 52,890