Acquisitions (Schedule of Acquisition) (Details) - USD ($) $ in Millions	Apr. 01, 2016	Jan. 15, 2016	Dec. 31, 2015	Feb. 23, 2015	Jan. 01, 2015	Jul. 01, 2014	May 16, 2014	Mar. 04, 2014	Oct. 02, 2013	Oct. 01, 2013	Aug. 01, 2013	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2014
Business Acquisition [Line Items]
Acquisition date		Jan. 15, 2016
Other current assets	$ 0.6
Property and equipment	15.4
Deferred tax assets, net	0.2
Intangibles	9.8
Goodwill	3.9											$ 1,214.5	$ 1,224.4	$ 866.7
Other assets	0.2
Total assets acquired	30.1
Current liabilities	1.1
Deferred revenue	0.4
Other liabilities	10.3
Total liabilities assumed	11.8
Net assets acquired	18.3
Net consideration paid	$ 18.3
Clearview
Business Acquisition [Line Items]
Acquisition date	Apr. 01, 2016
Allstream
Business Acquisition [Line Items]
Cash		$ 2.9
Other current assets		102.3
Property and equipment		269.2
Deferred tax assets, net		2.4
Intangibles		57.2
Other assets		4.6
Total assets acquired		438.6
Current liabilities		64.4
Deferred revenue		46.2
Other liabilities		27.5
Total liabilities assumed		138.1
Net assets acquired		300.5
Less cash acquired		(2.9)
Net consideration paid		$ 297.6
Viatel
Business Acquisition [Line Items]
Acquisition date			Dec. 31, 2015
Cash			$ 3.5
Other current assets			13.5
Property and equipment			162.3
Goodwill			13.0
Other assets			2.1
Total assets acquired			194.4
Current liabilities			17.6
Deferred revenue			57.8
Deferred tax liability, net			5.7
Other liabilities			7.1
Total liabilities assumed			88.2
Net assets acquired			106.2
Less cash acquired			(3.5)
Net consideration paid			$ 102.7
Dallas Data Center
Business Acquisition [Line Items]
Acquisition date			Dec. 31, 2015
Property and equipment			$ 14.8
Intangibles			1.8
Total assets acquired			16.6
Net assets acquired			16.6
Net consideration paid			$ 16.6
Atlanta NAP
Business Acquisition [Line Items]
Acquisition date						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
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						$ 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
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
Corelink Data Centers, LLC
Business Acquisition [Line Items]
Acquisition date											Aug. 01, 2013
Cash											$ 0.1
Other current assets											0.5
Property and equipment											15.9
Intangibles											0.2
Goodwill											2.9
Other assets											0.5
Total assets acquired											20.1
Current liabilities											0.7
Deferred revenue											0.2
Capital lease obligations											14.2
Deferred tax liability, net											3.0
Total liabilities assumed											18.1
Net assets acquired											2.0
Less cash acquired											(0.1)
Net consideration paid											$ 1.9
Access Communications, Inc
Business Acquisition [Line Items]
Acquisition date										Oct. 01, 2013
Cash										$ 1.2
Other current assets										2.3
Property and equipment										11.5
Intangibles										18.0
Goodwill										24.0
Total assets acquired										57.0
Current liabilities										1.0
Deferred revenue										5.1
Deferred tax liability, net										9.6
Total liabilities assumed										15.7
Net assets acquired										41.3
Less cash acquired										(1.2)
Net consideration paid										$ 40.1
Fiberlink, LLC
Business Acquisition [Line Items]
Acquisition date									Oct. 02, 2013
Other current assets									$ 0.8
Property and equipment									15.9
Deferred tax assets, net									7.7
Intangibles									19.3
Goodwill									19.8
Other assets									0.1
Total assets acquired									63.6
Current liabilities									1.3
Deferred revenue									19.2
Total liabilities assumed									20.5
Net assets acquired									43.1
Net consideration paid									$ 43.1
CoreXchange
Business Acquisition [Line Items]
Acquisition date								Mar. 04, 2014
Other current assets								$ 0.6
Property and equipment								3.1
Deferred tax assets, net								0.2
Intangibles								11.0
Goodwill								3.4
Total assets acquired								18.3
Current liabilities								0.5
Deferred revenue								0.4
Capital lease obligations								0.2
Total liabilities assumed								1.1
Net assets acquired								17.2
Net consideration paid								$ 17.2
Geo Networks Limited [Member]
Business Acquisition [Line Items]
Acquisition date							May 16, 2014
Cash							$ 13.7
Other current assets							8.8
Property and equipment							220.4
Intangibles							60.8
Goodwill							113.8
Other assets							9.8
Total assets acquired							427.3
Current liabilities							34.8
Deferred revenue							45.1
Deferred tax liability, net							38.2
Other liabilities							3.2
Total liabilities assumed							121.3
Net assets acquired							306.0
Less cash acquired							(13.7)
Net consideration paid							$ 292.3