Employee Benefit Plans (Narratives) (Details)				3 Months Ended		12 Months Ended					67 Months Ended
	Nov. 08, 2018 shares	Feb. 01, 2016 shares	Aug. 27, 2014 shares	Mar. 31, 2019 Quarter $ / shares	Sep. 30, 2018 $ / shares shares	Jun. 30, 2019 USD ($) Quarter $ / shares shares	Jun. 30, 2018 USD ($) Quarter $ / shares shares	Jun. 30, 2017 USD ($) $ / shares shares	Jun. 30, 2016	Nov. 20, 2013 shares	Jun. 30, 2019 USD ($) shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares outstanding for options and awards						2,719,000	2,193,000				2,719,000
Total intrinsic value of options exercised | $						$ 800,000	$ 6,300,000	$ 5,700,000
Awards granted						852,000	0	0
Weighted-average estimated fair value of options granted (in dollars per share) | $ / shares						$ 2.62
Total unrecognized compensation cost for unvested stock options | $						$ 1,000,000.0					$ 1,000,000.0
Stock options/units granted, grant date fair value | $ / shares						$ 6.39
Restricted stock units granted						4,698,000
Unrecognized compensation costs for non-vested stock awards | $						$ 29,100,000					$ 29,100,000
401(k) Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum annual contributions per employee | $						19,000
Additional annual contribution per employee over age of 50 | $						$ 6,000
Employer matching contribution per dollar contributed by employee						0.50%
Maximum employer matching contribution of employee total compensation (percent)						2.50%
Matching contributions to the Plan | $						$ 4,200,000	$ 3,300,000	$ 1,400,000
Employer discretionary contributions | $						$ 0	0	0
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, award vesting percentage						The RSUs vest from the original grant date as to one-third (1/3) on the one-year anniversary and one-twelfth (1/12) each quarter thereafter, subject to continued service to the Company.
Aggregate fair value, as of the respective vesting dates | $						$ 30,000,000.0	$ 51,200,000	$ 9,100,000
Restricted stock units granted, percentage							40.00%
Aggregate shares withheld upon vesting						1,300,000	1,000,000.0	400,000
Cash remitted to the appropriate taxing authorities | $						$ 8,400,000	$ 11,300,000	$ 2,000,000.0
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options/units granted, grant date fair value | $ / shares						$ 6.40	$ 10.90
Awards granted, value | $						$ 600,000
Performance stock unit vesting, consecutive quarters | Quarter				2
Restricted stock units granted						0
Performance stock unit vesting, earnings per share threshold one | $ / shares				$ 0.32
Performance stock unit vesting, earnings per share threshold two | $ / shares				$ 0.20
Expected volatility rate								56.00%
Risk free rate								0.90%
Expected dividend yield								0.00%
Expected term								3 years
Performance Shares | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options/units granted, grant date fair value | $ / shares								$ 3.02
Performance Shares | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options/units granted, grant date fair value | $ / shares								$ 3.09
Service-based Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units granted, percentage							50.00%	50.00%
Market-Based Vesting | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options/units granted, grant date fair value | $ / shares							$ 10.61
Market-Based Vesting | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options/units granted, grant date fair value | $ / shares							12.19
Stock Price PSU
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units granted, percentage								50.00%
Stock Price PSU | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Average adjusted closing stock price | $ / shares						$ 8.96
Stock Price PSU | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting percentage						133.33%
TSR PSU
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units granted, percentage								50.00%
Expected volatility rate						54.00%
Risk free rate						1.50%
Expected dividend yield						0.00%
Expected term						3 years
Shares earned, Maximum						130.00%
Shares earned, Target						100.00%
TSR PSU | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options/units granted, grant date fair value | $ / shares						$ 7.01
TSR PSU | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options/units granted, grant date fair value | $ / shares						$ 8.76
Non-vested Stock Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognition period for compensation cost not yet recognized (in years, months, and days)						1 year 7 months 6 days
Certain Officers and Executive Vice Presidents | Performance Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards granted					851,700
Stock options/units vesting, stock trigger price | $ / shares					$ 10.00
Stock options vesting performance period					3 years
Stock options vesting, Threshold consecutive trading days from August 29, 2018 through August 31, 2021					30 days
Stock options/units granted, grant date fair value | $ / shares						$ 2.62
Certain Officers and Executive Vice Presidents | Performance Stock Options | Price Hurdle Met Before or on August 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting percentage						33.33%
Share-based compensation arrangement by share-based payment award, award vesting percentage						one-third of the PSOs will vest on August 31, 2019 and the remainder will vest quarterly over two years.
Certain Officers and Executive Vice Presidents | Performance Stock Options | Price Hurdle Met After August 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, award vesting percentage						a number of the PSOs will vest (ratably calculated based upon the time elapsed between August 31, 2018 and the date the hurdle is met) and the remainder will vest quarterly through August 31, 2021.
Executive Officers and Directors
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards granted, value | $						$ 900,000
Executive Officers and Directors | Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards granted, value | $						200,000
Executive Officers and Directors | Service-based Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards granted, value | $						700,000
Other Vice President Level Employees | Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards granted, value | $						$ 400,000
Employees | Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options/units vesting, stock trigger price | $ / shares						$ 10.00	$ 16.00	$ 5.00
Stock options vesting, Threshold consecutive trading days from August 29, 2018 through August 31, 2021								30 days
Performance stock unit vesting, consecutive quarters | Quarter						2	2
Employees | Performance Shares | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance stock unit vesting, earnings per share | $ / shares						$ 0.20	$ 0.32
Execs | Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units granted							1,200,000	1,500,000
Execs | Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units granted								1,400,000
Restricted stock units granted, percentage							50.00%	50.00%
Execs | Market-Based Vesting
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units granted							100,000
Named Executive Officers | Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units granted							600,000	700,000
Named Executive Officers | Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units granted								900,000
Chief Executive Officers | Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units granted, percentage							60.00%
Non-Executives
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Estimated forfeiture rate									13.00%
Executives
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Estimated forfeiture rate									19.00%
2013 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Authorized shares for issuance										9,000,000.0
Shares subject to previously expired awards reinstated										12,700,000
Decrease in shares available for future grants for each Full Value Award awarded										1.50%
Additional authorized shares for issuance							9,000,000.0
Employee stock options and stock awards available for grant						8,500,000					8,500,000
Shares outstanding for options and awards						9,700,000					9,700,000
Contractual term						7 years
Shares transferred from 2005 plan to 2013 plan											6,600,000
Enterasys Networks Inc. 2013 Stock Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee stock options and stock awards available for grant						0					0
Shares outstanding for options and awards						700,000					700,000
Contractual term						7 years
2005 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Decrease in shares available for future grants for each Full Value Award awarded						1.50%
Employee stock options and stock awards available for grant						0					0
Shares included in outstanding options						100,000					100,000
2014 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Authorized shares for issuance			12,000,000.0			9,400,000					9,400,000
Additional authorized shares for issuance	7,500,000
Weighted-average estimated fair value of options granted (in dollars per share) | $ / shares						$ 2.71	$ 3.25	$ 1.24
Maximum offering period per purchase period (in months)						6 months
Maximum of total compensation permitted to acquire shares (percent)			15.00%
Percent of fair market value for price per share to employees (percent)			85.00%
Shares issued under stock purchase plan						2,800,000	2,400,000
Maximum shares issuable for each purchase period		1,500,000	1,000,000.0
2014 Employee Stock Purchase Plan | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Offering periods (in months)							6 months
2014 Employee Stock Purchase Plan | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Offering periods (in months)							24 months