Financial Information of Company's Operation by Segment (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Jun. 30, 2017
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
Revenues	$ 281,470	$ 231,822	$ 542,973	$ 453,342
Operating income	32,547	27,136	62,324	50,827
Interest expense	(4,644)	(1,365)	(8,289)	(2,611)
Other income (expense), net	1,965	6,045	2,732	7,447
Income taxes	(20,272)	(7,913)	(26,030)	(15,466)
Net earnings	9,596	23,903	30,737	40,197
Depreciation and amortization	19,409	14,916	38,225	29,798
Segment assets	1,687,874		1,687,874		$ 1,477,297
Expenditures for property, plant & equipment	39,397	27,828	76,823	57,822
Investments	67,068		67,068		$ 11,727
Operating Segments | II-VI Laser Solutions
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
Revenues	109,817	81,483	203,079	160,773
Inter-segment revenues	6,830	8,760	14,014	14,700
Operating income	9,493	7,593	12,757	14,291
Depreciation and amortization	8,948	5,662	17,254	11,312
Segment assets	721,491		721,491
Expenditures for property, plant & equipment	23,920	15,737	37,176	35,862
Operating Segments | II-VI Photonics
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
Revenues	110,520	100,906	221,134	196,725
Inter-segment revenues	6,914	3,161	11,492	6,599
Operating income	16,930	15,901	36,429	29,791
Depreciation and amortization	6,568	4,976	12,731	9,824
Segment assets	584,771		584,771
Expenditures for property, plant & equipment	9,038	5,900	19,616	12,497
Operating Segments | II- VI Performance Products
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
Revenues	61,133	49,433	118,760	95,844
Inter-segment revenues	1,157	2,645	1,984	4,378
Operating income	6,124	3,642	13,138	6,745
Depreciation and amortization	3,893	4,278	8,240	8,662
Segment assets	381,612		381,612
Expenditures for property, plant & equipment	6,439	6,191	20,031	9,463
Investments	67,068		67,068
Eliminations
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
Inter-segment revenues	$ (14,901)	$ (14,566)	$ (27,490)	$ (25,677)