Acquisitions (Narrative) (Details) In Millions, except Share data, unless otherwise specified	3 Months Ended		89 Months Ended	0 Months Ended		3 Months Ended					0 Months Ended	3 Months Ended		0 Months Ended		3 Months Ended	12 Months Ended		0 Months Ended	3 Months Ended	0 Months Ended	12 Months Ended			0 Months Ended		3 Months Ended	12 Months Ended	0 Months Ended	12 Months Ended	0 Months Ended	12 Months Ended
	Sep. 30, 2014 USD ($)	Sep. 30, 2013 USD ($)	Sep. 30, 2014 business_combination	May 01, 2014 Neo Telecoms [Member] USD ($)	May 01, 2014 Neo Telecoms [Member] EUR (€)	Sep. 30, 2014 Neo Telecoms [Member]	Sep. 30, 2014 Neo Telecoms [Member] USD ($)	Jun. 30, 2014 Neo Telecoms [Member] USD ($)	Jun. 30, 2014 Neo Telecoms [Member] EUR (€)	Jun. 30, 2014 Neo Telecoms [Member] Call Option [Member]	Jul. 03, 2014 Atlanta NAP [Member] USD ($)	Sep. 30, 2014 Atlanta NAP [Member]	Jun. 30, 2014 Atlanta NAP [Member] USD ($)	Aug. 01, 2013 Colocation Acquisition [Member] USD ($)	Oct. 02, 2013 Access [Member] USD ($)	Sep. 30, 2014 Access [Member] USD ($)	Jun. 30, 2014 Access [Member]	Oct. 01, 2013 Access [Member] USD ($)	Oct. 02, 2013 Fiberlink, LLC [Member] USD ($)	Sep. 30, 2014 Fiberlink, LLC [Member] USD ($)	Mar. 04, 2014 CoreXchange [Member] USD ($)	Jun. 30, 2014 CoreXchange [Member]	Sep. 30, 2014 CoreXchange [Member] USD ($)	Mar. 31, 2014 CoreXchange [Member]	May 16, 2014 Geo [Member] USD ($)	May 16, 2014 Geo [Member] GBP (£)	Sep. 30, 2014 Geo [Member] USD ($)	Jun. 30, 2014 Geo [Member]	Aug. 01, 2013 CoreLink [Member] USD ($)	Jun. 30, 2014 CoreLink [Member]	Oct. 02, 2013 FiberLink [Member] USD ($)	Jun. 30, 2014 FiberLink [Member]	Sep. 30, 2014 FiberLink [Member] USD ($)
Business Acquisition [Line Items]
Number of business combinations completed			32
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%
Consideration of acquiring equity ownership				$ 78.1	€ 57.2						$ 52.5			$ 0.3											$ 292.3	£ 174.3
Escrow deposit								11.9	8.7
Purchase price, held in escrow											5.3				4.0						1.8
Net assets acquired													52.5	1.9				41.3			17.5				306.0				2.0		43.1
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							73.9				52.5				40.1				43.1		17.5				292.3				1.9		43.1
Notes payable																										113.4
Notes payable, related parties																										69.1
Intangibles assumed								13.4					30.4			18.0		18.0			10.1		10.1		61.2		61.2		0.2		19.3		19.3
Estimated useful life of acquired intangible assets						15 years						11 years					20 years					11 years						12 years		12 years		18 years
Deferred revenue acquired													0.3					5.1			0.4				44.3		44.3		0.2		19.2
Business combination, deferred revenue, weighted average remaining contractual term																											9 years 8 months 12 days
Deferred Tax Assets, Net																									(38.0)		38.0
Property plant and equipment purchase accounting adjustments																3.1				9.9
Finite lived intangible assets, purchase accounting adjustments																2.0				2.1
Deferred tax assets purchase accounting adjustments																2.0				0.7
Acquisition related costs	$ 3.4	$ 0.6