Acquisitions (Narrative) (Detail) In Millions, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended		95 Months Ended	0 Months Ended		9 Months Ended				0 Months Ended	9 Months Ended		0 Months Ended		9 Months Ended		0 Months Ended	9 Months Ended	0 Months Ended		3 Months Ended	9 Months Ended	0 Months Ended		3 Months Ended	9 Months Ended		0 Months Ended	3 Months Ended	9 Months Ended		0 Months Ended		9 Months Ended		0 Months Ended		9 Months Ended		0 Months Ended	9 Months Ended	3 Months Ended
	Mar. 31, 2015 USD ($)	Mar. 31, 2014 USD ($)	Mar. 31, 2015 USD ($)	Mar. 31, 2014 USD ($)	Mar. 31, 2015 USD ($) Acquisition	Jul. 03, 2014 Neo Telecoms [Member] USD ($)	Jul. 03, 2014 Neo Telecoms [Member] EUR (€)	Mar. 31, 2015 Neo Telecoms [Member] USD ($)	Jul. 01, 2014 Neo Telecoms [Member] USD ($)	Jul. 01, 2014 Neo Telecoms [Member] EUR (€)	Jul. 01, 2014 Neo Telecoms [Member] Call Option [Member]	Jul. 03, 2014 Atlanta NAP [Member] USD ($)	Mar. 31, 2015 Atlanta NAP [Member] USD ($)	Jul. 01, 2014 Atlanta NAP [Member] USD ($)	Jan. 06, 2015 IdeaTek [Member] USD ($) mi Buildings CellularTowers	Jan. 03, 2015 IdeaTek [Member]	Mar. 31, 2015 IdeaTek [Member] USD ($)	Jan. 01, 2015 IdeaTek [Member] USD ($)	Aug. 01, 2013 Corelink [Member] USD ($)	Mar. 31, 2015 Corelink [Member]	Oct. 02, 2013 Access acquisition [Member] USD ($)	Oct. 01, 2013 Access acquisition [Member] USD ($)	Sep. 30, 2014 Access acquisition [Member] USD ($)	Mar. 31, 2015 Access acquisition [Member] USD ($)	Oct. 02, 2013 Fiber Link [Member] USD ($)	Oct. 02, 2013 Fiber Link [Member] USD ($)	Sep. 30, 2014 Fiber Link [Member] USD ($)	Mar. 31, 2015 Fiber Link [Member] USD ($)	Mar. 31, 2014 Fiber Link [Member] USD ($)	Mar. 04, 2014 CoreXchange [Member] USD ($)	Mar. 31, 2015 CoreXchange [Member] USD ($)	Mar. 31, 2015 CoreXchange [Member] USD ($)	Mar. 31, 2014 CoreXchange [Member] USD ($)	May 16, 2014 Geo [Member] USD ($)	May 16, 2014 Geo [Member] GBP (£)	Mar. 31, 2015 Geo [Member] USD ($)	Dec. 31, 2014 Geo [Member] USD ($)	Feb. 25, 2015 Latisys Holdings [Member] USD ($)	Feb. 23, 2015 Latisys Holdings [Member] USD ($) MW sqft DataCentre Market	Mar. 31, 2015 Latisys Holdings [Member] USD ($)	Dec. 31, 2014 Latisys Holdings [Member] USD ($)	Aug. 31, 2012 Fibergate Holdings Inc [Member] USD ($)	Mar. 31, 2015 Fibergate Holdings Inc [Member]	Dec. 31, 2014 Fibergate Holdings Inc [Member] Selling, General and Administrative Expenses [Member] USD ($)
Business Acquisition [Line Items]
Number of business combinations completed					34
Acquisition date			Jul. 01, 2014									Jul. 01, 2014	Jul. 01, 2014			Jan. 01, 2015	Jan. 06, 2015		Aug. 01, 2013	Aug. 01, 2013		Oct. 01, 2013		Oct. 01, 2013	Oct. 02, 2013			Oct. 02, 2013		Mar. 04, 2014		Mar. 04, 2014		May 16, 2014	May 16, 2014	May 16, 2014		Feb. 23, 2015		Feb. 23, 2015			Aug. 31, 2012
Business acquisition, percentage of voting interests acquired									96.00%	96.00%	4.00%			100.00%							100.00%				100.00%	100.00%							100.00%	100.00%	100.00%							100.00%
Cash paid for acquisitions, net of cash acquired						$ 73.9	€ 54.1	$ 73.9				$ 52.5			$ 53.6				$ 1.9		$ 40.1	$ 40.1			$ 43.1	$ 43.1			$ 43.1	$ 17.2		$ (0.3)	$ 17.5	$ 292.3	£ 174.3			$ 677.5	$ 677.5	$ 677.5
Escrow deposit									11.9	8.7
Purchase price, held in escrow												5.3			3.2						4.0									1.8									31.4			17.6
Net assets acquired																			1.9
Business acquisition, equity interest issued or issuable, number of shares																			301,949
Business acquisition, equity interest issued or issuable, value assigned																			1.6
Cash paid for acquisitions, net of cash acquired																			0.3
Notes payable																																			113.4
Notes payable, related parties																																			69.1
Intangibles								26.0					21.0	21.0			24.0	24.0	0.2			18.0		18.0	19.3	19.3		19.3		11.0	11.0	11.0		61.2		41.4			243.2	243.2
Estimated useful life of acquired intangible assets								19 years					15 years				19 years							20 years				18 years				12 years								15 years
Deferred Tax Assets, Net																																		(38.9)			38.9		(76.5)		(76.5)
Property plant and equipment purchase accounting adjustments																							3.1				9.9				0.2
Finite lived intangible assets, purchase accounting adjustments																							2.0				2.1				0.9
Deferred tax assets purchase accounting adjustments																							2.0				0.7
Other current assets purchase accounting adjustments			1.9																												0.4
Current liabilities purchase accounting adjustments			8.7																												0.1
Consideration of acquiring equity ownership																																										118.3
Refund of purchase price																																												2.5
Property and equipment accounting adjustments			1.7
Other assets purchase accounting adjustments			0.1
Deferred revenue purchase accounting adjustments			3.6
Deferred tax liabilities purchase accounting adjustments			1.4
Other liabilities accounting adjustments	3.7		3.7		3.7
Acquisition related costs	$ 1.5	$ 0	$ 6.2	$ 0.8
Additional Route Miles Acquired															1,800
Number Of Additional Cellular Towers Acquired															600
Number Of Additional Building Acquired															100
Acquired area in square feet																																							185,000
Critical power acquired																																							33
Number of data center																																							8
Number of market																																							5