Acquisitions (Schedule of Acquisition) (Details) € in Millions, $ in Millions								6 Months Ended
	Dec. 31, 2015 EUR (€)	Dec. 31, 2015 USD ($)	Feb. 23, 2015 USD ($)	Jan. 01, 2015 USD ($)	Jul. 03, 2014	Jul. 01, 2014 EUR (€)	Jul. 01, 2014 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Jun. 30, 2015 USD ($)
Business Acquisition [Line Items]
Goodwill		$ 1,222.2						$ 1,222.2		$ 1,224.4
Viatel [ Member ]
Business Acquisition [Line Items]
Acquisition date	Dec. 31, 2015	Dec. 31, 2015
Cash		$ 5.3						5.3
Other current assets		7.5						7.5
Property and equipment		127.2						127.2
Intangibles		24.8						24.8
Goodwill		12.1						12.1
Total assets acquired		176.9						176.9
Current liabilities		14.4						14.4
Deferred revenue		46.6						46.6
Deferred tax liability, net		9.6						9.6
Total liabilities assumed		70.6						70.6
Net assets acquired		106.3						106.3
Less cash acquired		(5.3)						(5.3)
Net consideration paid	€ 92.6	101.0							$ 73.9
Dallas Data Center [Member]
Business Acquisition [Line Items]
Property and equipment		14.9						14.9
Intangibles		1.8						1.8
Total assets acquired		16.7						16.7
Net assets acquired		16.7						16.7
Net consideration paid		$ 16.7						16.7	$ 52.5
Atlanta NAP [Member]
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
Neo Telecoms [Member]
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	$ 101.0
Ideatek Systems, Inc., [Member]
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 [Member]
Business Acquisition [Line Items]
Acquisition date			Feb. 23, 2015
Cash			$ 9.4
Other current assets			17.2
Property and equipment			222.9
Deferred tax assets, net			0.4
Intangibles			250.2
Goodwill			274.7
Other assets			5.0
Total assets acquired			779.8
Current liabilities			10.0
Deferred revenue			3.1
Deferred tax liability, net			79.5
Total liabilities assumed			92.6
Net assets acquired			687.2
Less cash acquired			(9.4)
Net consideration paid			$ 677.8