Acquisitions and Investment - Additional Information (Detail) - USD ($)	1 Months Ended		2 Months Ended	3 Months Ended	6 Months Ended
	Aug. 31, 2017	Jun. 30, 2017	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 13, 2017	Nov. 30, 2017
Business Acquisition [Line Items]
Equity interest acquired			93.80%	93.80%	93.80%			93.80%
Aggregate cost of equity method investments								$ 51,500,000
Pro-rata share of earnings from equity method investment			$ 1,100,000		$ 1,617,000	$ 490,000
Voting interest					25.00%
Investments		$ 11,727,000	67,068,000	$ 67,068,000	$ 67,068,000
Purchase price description of minority interest under equity method					The purchase price is equal to the greater of: (a) (i) the product of the aggregate trailing 12-month revenues of the investment preceding the date of purchase, multiplied by (ii) a factor of 2.9 multiplied by (iii) a factor of 0.723, multiplied by (iv) the percentage interest owned by each minority equity holder and (b) $966,666
Minimum purchase price consideration of remaining minority interest under equity method			966,666	966,666	$ 966,666
Goodwill		250,342,000	272,209,000	272,209,000	272,209,000
II-VI Laser Solutions Segment
Business Acquisition [Line Items]
Goodwill		84,180,000	104,541,000	104,541,000	104,541,000
II-VI Photonics Segment
Business Acquisition [Line Items]
Goodwill		113,272,000	114,778,000	114,778,000	114,778,000
II-VI Compound Semiconductor Ltd (Kaiam Laser Limited, Inc)
Business Acquisition [Line Items]
Net cash paid at acquisition	$ 79,500,000
Goodwill	19,670,000
Business acquisition, transaction costs			600,000	600,000	600,000
Business acquisition, revenue of acquired entity				1,000,000	1,600,000
Business acquisition, (loss) earnings of acquired entity				(2,500,000)	(6,200,000)
II-VI Compound Semiconductor Ltd (Kaiam Laser Limited, Inc) | II-VI Laser Solutions Segment
Business Acquisition [Line Items]
Goodwill	$ 19,700,000
Integrated Photonics, Inc
Business Acquisition [Line Items]
Net cash paid at acquisition		40,098,000
Goodwill		17,503,000
Business acquisition, transaction costs		300,000
Business acquisition, revenue of acquired entity				4,900,000	10,300,000
Business acquisition, (loss) earnings of acquired entity				1,000,000	1,400,000
Payment of additional amount for working capital adjustment		837,000
Fair value of accounts receivable acquired		2,100,000
Fair value of accounts receivable gross contractual amount		2,100,000
Integrated Photonics, Inc | Upon Achievement of Financial And Transitional Objectives Relating to Finance Information Technology And Human Resources
Business Acquisition [Line Items]
Business acquisitions, contingent consideration, current		2,500,000
Integrated Photonics, Inc | Upon Achievement of Financial And Transitional Objectives Relating to Finance Information Technology And Human Resources | Maximum
Business Acquisition [Line Items]
Business acquisitions, contingent consideration		2,500,000
Integrated Photonics, Inc | II-VI Photonics Segment
Business Acquisition [Line Items]
Goodwill		$ 17,500,000
Other Long-term Liabilities | ASC 815-10, Derivatives and Hedging
Business Acquisition [Line Items]
Equity method Investment, noncurrent liabilities			2,200,000	2,200,000	2,200,000		$ 2,200,000
Equity Investment
Business Acquisition [Line Items]
Investments			$ 54,800,000	$ 54,800,000	$ 54,800,000