Income Taxes (Narratives) (Details) - USD ($) $ in Thousands	12 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2014
Operating Loss Carryforwards [Line Items]
Change in valuation allowance for fiscal year	$ 18,000	$ 3,800
Federal tax net operating loss carry-forwards	291,300
State tax net operating loss carry-forwards	93,700
Tax credit carry-forwards	34,444	32,730	$ 30,824
Amount of earnings to be reinvested indefinitely of certain foreign corporations	11,500
Unrecognized income tax (benefit) for undistributed foreign earnings	200
Unrecognized tax benefits	18,913	11,653	11,359	$ 11,600
Estimated interest and penalties related to underpayment of income taxes, less than	$ 100	$ 100	$ 100
Enterasys Networks, Inc.
Operating Loss Carryforwards [Line Items]
Amortization period of intangible assets and goodwill resulting from acquisition				15 years
Zebra Technologies Corporation
Operating Loss Carryforwards [Line Items]
Amortization period of intangible assets and goodwill resulting from acquisition	15 years
MTS IRELAND
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	$ 46,700
CITI MATCH AUSTRALIA
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	9,800
BRAZILIAN ENERGY EXCHANGE
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	7,300
INSTINET JAPAN
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	300
Foreign
Operating Loss Carryforwards [Line Items]
Tax credit carry-forwards	8,100
State
Operating Loss Carryforwards [Line Items]
Tax credit carry-forwards	16,400
State | Subject To Expiration
Operating Loss Carryforwards [Line Items]
Tax credit carry-forwards	900
State | Not Subject To Expiration
Operating Loss Carryforwards [Line Items]
Tax credit carry-forwards	15,500
Federal
Operating Loss Carryforwards [Line Items]
Tax credit carry-forwards	23,800
Federal | Subject To Expiration
Operating Loss Carryforwards [Line Items]
Tax credit carry-forwards	$ 15,500