Summary of Significant Accounting Policies (Narratives) (Details)		3 Months Ended		12 Months Ended
	Oct. 31, 2013 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Jun. 30, 2015 USD ($) Distribution_Channels	Jun. 30, 2014 USD ($) Investment_Securities	Jun. 30, 2013 USD ($)
Significant Accounting Policies [Line Items]
Deferred product revenue from customers other than distributors		$ 99,782,000		$ 99,782,000	$ 97,677,000
Number of distribution channels | Distribution_Channels				2
Inventory, net		58,014,000		$ 58,014,000	$ 57,109,000
Number of securities with unrealized losses (in securities) | Investment_Securities					2
Number of investment securities (in securities) | Investment_Securities					18
Other-than-temporary impairment loss					$ 158,000
Long-term debt, carrying amount		66,875,000		66,875,000	66,900,000
Long-term debt, estimated fair value		121,600,000		121,600,000	121,600,000
Purchases of non-marketable equity investments			$ 3,000,000	3,000,000	0	$ 0
Goodwill acquired in period				0	70,877,000
Amortization expense				35,900,000	28,800,000	1,500,000
Service inventory held to support customers		18,100,000		18,100,000	11,400,000
Increase (decrease) in commitment amount		(10,000,000.0)
Deferred financing costs		500,000		500,000	1,300,000
Amortization of deferred financing costs		400,000		400,000	200,000
Outstanding letters of credit		900,000		$ 900,000	900,000
Standard hardware warranty period (in months)				12 months
Standard software warranty period (in days)				90 days
Limited lifetime hardware warranty maximum period after end of sale of product (in years)				5 years
Advertising expenses				$ 500,000	500,000	200,000
Revolving Credit Facility
Significant Accounting Policies [Line Items]
Borrowing capacity from Credit Agreement	$ 60,000,000	50,000,000		$ 50,000,000
Credit Agreement term	5 years			5 years
Term Loan Facility
Significant Accounting Policies [Line Items]
Borrowing capacity from Credit Agreement	$ 65,000,000
Credit Agreement term	5 years
Senior Secured Credit Facilities
Significant Accounting Policies [Line Items]
Borrowing capacity from Credit Agreement		$ 115,000,000.0		$ 115,000,000.0
Commitment fee percentage		0.50%
Senior Secured Credit Facilities | Federal funds effective rate
Significant Accounting Policies [Line Items]
Basis spread on variable rate		0.75%
Enterasys Networks, Inc.
Significant Accounting Policies [Line Items]
Increase in property and equipment for asset retirement obligations					1,200,000
Enterasys Networks, Inc. | Revolving Credit Facility
Significant Accounting Policies [Line Items]
Draw downs from Revolving Facility	$ 35,000,000
Cost Of Product Revenue
Significant Accounting Policies [Line Items]
Amortization expense				$ 17,200,000	11,900,000	1,500,000
Minimum
Significant Accounting Policies [Line Items]
Extended warranty contracts period (in years)				1 year
Minimum | Senior Secured Credit Facilities
Significant Accounting Policies [Line Items]
Commitment fee percentage		0.375%
Maximum
Significant Accounting Policies [Line Items]
Extended warranty contracts period (in years)				5 years
Maximum | Senior Secured Credit Facilities
Significant Accounting Policies [Line Items]
Commitment fee percentage		0.50%
Computer Equipment | Minimum
Significant Accounting Policies [Line Items]
Estimated useful lives of property and equipment				1 year
Computer Equipment | Maximum
Significant Accounting Policies [Line Items]
Estimated useful lives of property and equipment				4 years
Purchased Software | Minimum
Significant Accounting Policies [Line Items]
Estimated useful lives of property and equipment				1 year
Purchased Software | Maximum
Significant Accounting Policies [Line Items]
Estimated useful lives of property and equipment				4 years
Office Equipment | Minimum
Significant Accounting Policies [Line Items]
Estimated useful lives of property and equipment				3 years
Office Equipment | Maximum
Significant Accounting Policies [Line Items]
Estimated useful lives of property and equipment				7 years
Leasehold Improvements | Minimum
Significant Accounting Policies [Line Items]
Estimated useful lives of property and equipment				2 years
Leasehold Improvements | Maximum
Significant Accounting Policies [Line Items]
Estimated useful lives of property and equipment				10 years
Available-for-sale Securities | Government and Corporate Debt Securities
Significant Accounting Policies [Line Items]
Maturity period for investments (in months and years)				3 years
Marketable Securities | Minimum
Significant Accounting Policies [Line Items]
Maturity period for investments (in months and years)				1 year
Product
Significant Accounting Policies [Line Items]
Deferred revenue from customers other than distributors		$ 6,100,000		$ 6,100,000	4,100,000
Service revenue, renewable support arrangements
Significant Accounting Policies [Line Items]
Deferred product revenue from customers other than distributors		$ 87,441,000		$ 87,441,000	$ 89,657,000	$ 38,003,000