Acquisitions (Narrative) (Details) € in Millions, $ in Millions								3 Months Ended		6 Months Ended
	Dec. 31, 2015 EUR (€) item	Dec. 31, 2015 USD ($) item	Feb. 23, 2015 USD ($)	Jan. 01, 2015 USD ($) building item mi	Jul. 03, 2014	Jul. 01, 2014 EUR (€)	Jul. 01, 2014 USD ($)	Dec. 31, 2015 USD ($) item	Dec. 31, 2014 USD ($)	Dec. 31, 2015 USD ($) item	Dec. 31, 2014 USD ($)
Business Acquisition [Line Items]
Number of business combinations completed | item										36
Acquisition related costs								$ 3.3	$ 1.3	$ 3.3	$ 4.8
Viatel [ Member ]
Business Acquisition [Line Items]
Acquisition date	Dec. 31, 2015	Dec. 31, 2015
Business acquisition, percentage of voting interests acquired	100.00%	100.00%						100.00%		100.00%
Cash paid for acquisitions, net of cash acquired	€ 92.6	$ 101.0									73.9
Purchase price, held in escrow	€ 5.0	5.5
Dallas Data Center [Member]
Business Acquisition [Line Items]
Cash paid for acquisitions, net of cash acquired		$ 16.7								$ 16.7	$ 52.5
Acquired facility size (in square feet) | item	36,000	36,000						36,000		36,000
Atlanta NAP [Member]
Business Acquisition [Line Items]
Acquisition date						Jul. 01, 2014	Jul. 01, 2014
Business acquisition, percentage of voting interests acquired							100.00%
Cash paid for acquisitions, net of cash acquired							$ 51.9
Neo Telecoms [Member]
Business Acquisition [Line Items]
Acquisition date					Jul. 01, 2014
Business acquisition, percentage of voting interests acquired							96.00%
Cash paid for acquisitions, net of cash acquired						€ 54.1	$ 73.9			$ 101.0
Purchase price, held in escrow						€ 8.7	$ 11.9
Business acquisition percentage of non controlling interest							4.00%
Neo Telecoms [Member] | Other long-term liabilities
Business Acquisition [Line Items]
Business acquisition, fair value of non-controlling interest							$ 2.9
Neo Telecoms [Member] | Call Option [Member]
Business Acquisition [Line Items]
Business acquisition, percentage of voting interests acquired							4.00%
Ideatek Systems, Inc., [Member]
Business Acquisition [Line Items]
Acquisition date				Jan. 01, 2015
Cash paid for acquisitions, net of cash acquired				$ 52.7
Purchase price, held in escrow				$ 3.2
Additional Route Miles Acquired | mi				1,800
Number Of Additional Cellular Towers connected | item				600
Number Of Additional Building connected | building				100
Latisys Holdings, LLC [Member]
Business Acquisition [Line Items]
Acquisition date			Feb. 23, 2015
Cash paid for acquisitions, net of cash acquired			$ 677.8
Purchase price, held in escrow			$ 31.4