Acquisitions (Schedule of Acquisition) (Details) € in Millions, CAD in Millions, $ in Millions										9 Months Ended
	Jan. 15, 2016 CAD	Jan. 15, 2016 USD ($)	Dec. 31, 2015 EUR (€)	Dec. 31, 2015 USD ($)	Feb. 23, 2015 USD ($)	Jan. 01, 2015 USD ($)	Jul. 03, 2014	Jul. 01, 2014 EUR (€)	Jul. 01, 2014 USD ($)	Mar. 31, 2016 USD ($)	Mar. 31, 2015 USD ($)	Jun. 30, 2015 USD ($)
Business Acquisition [Line Items]
Goodwill										$ 1,219.6		$ 1,224.4
Allstream
Business Acquisition [Line Items]
Cash		$ 2.9
Other current assets		103.0
Property and equipment		268.7
Deferred tax assets, net		11.7
Intangibles		45.0
Other assets		6.9
Total assets acquired		438.2
Current liabilities		61.4
Deferred revenue		46.4
Other liabilities		29.9
Total liabilities assumed		137.7
Net assets acquired		300.5
Less cash acquired		(2.9)
Net consideration paid	CAD 422.9	$ 297.6								297.6
Viatel
Business Acquisition [Line Items]
Acquisition date			Dec. 31, 2015	Dec. 31, 2015
Cash				$ 3.5
Other current assets				8.0
Property and equipment				160.6
Goodwill				12.7
Other assets				4.5
Total assets acquired				189.3
Current liabilities				16.5
Deferred revenue				61.5
Other liabilities				5.1
Total liabilities assumed				83.1
Net assets acquired				106.2
Less cash acquired				(3.5)
Net consideration paid			€ 94.2	$ 102.7						102.7
Dallas Data Center
Business Acquisition [Line Items]
Acquisition date			Dec. 31, 2015	Dec. 31, 2015
Property and equipment				$ 14.9
Intangibles				1.8
Total assets acquired				16.7
Net assets acquired				16.7
Net consideration paid				$ 16.7						$ 16.7
Atlanta NAP
Business Acquisition [Line Items]
Acquisition date								Jul. 01, 2014	Jul. 01, 2014
Other current assets									$ 0.2
Property and equipment									7.0
Intangibles									21.0
Goodwill									25.2
Total assets acquired									53.4
Current liabilities									1.5
Total liabilities assumed									1.5
Net assets acquired									51.9
Net consideration paid									51.9		$ 52.5
Neo Telecoms
Business Acquisition [Line Items]
Acquisition date							Jul. 01, 2014
Cash									4.2
Other current assets									9.5
Property and equipment									31.3
Intangibles									26.4
Goodwill									32.5
Other assets									2.3
Total assets acquired									106.2
Current liabilities									13.5
Deferred revenue									3.7
Deferred tax liability, net									7.6
Other liabilities									3.3
Total liabilities assumed									28.1
Net assets acquired									78.1
Less cash acquired									(4.2)
Net consideration paid								€ 54.1	$ 73.9		73.9
Ideatek Systems, Inc
Business Acquisition [Line Items]
Acquisition date						Jan. 01, 2015
Other current assets						$ 0.8
Property and equipment						32.3
Deferred tax assets, net						3.1
Intangibles						7.6
Goodwill						39.0
Total assets acquired						82.8
Current liabilities						4.4
Deferred revenue						25.7
Total liabilities assumed						30.1
Net assets acquired						52.7
Net consideration paid						$ 52.7					53.6
Latisys Holdings, LLC
Business Acquisition [Line Items]
Acquisition date					Feb. 23, 2015
Cash					$ 9.4
Other current assets					17.4
Property and equipment					222.9
Deferred tax assets, net					0.4
Intangibles					250.2
Goodwill					274.1
Other assets					5.0
Total assets acquired					779.4
Current liabilities					9.9
Deferred revenue					3.2
Deferred tax liability, net					79.1
Total liabilities assumed					92.2
Net assets acquired					687.2
Less cash acquired					(9.4)
Net consideration paid					$ 677.8						677.5
CoreXchange
Business Acquisition [Line Items]
Net consideration paid											$ (0.3)