Segment Reporting (Narrative) (Details)	3 Months Ended
	Sep. 30, 2016 customer item
Dark Fiber Solutions [Member] | Minimum
Segment Reporting Information [Line Items]
Number of dark fiber pairs leased to customers	2
Contract term	3 years
Dark Fiber Solutions [Member] | Maximum
Segment Reporting Information [Line Items]
Number of dark fiber pairs leased to customers	12
Contract term	20 years
Network Connectivity [Member] | Minimum
Segment Reporting Information [Line Items]
Contract term	2 years
Network Connectivity [Member] | Maximum
Segment Reporting Information [Line Items]
Contract term	5 years
Colocation and Cloud Infrastructure [Member] | Minimum
Segment Reporting Information [Line Items]
Contract term	2 years
Colocation and Cloud Infrastructure [Member] | Maximum
Segment Reporting Information [Line Items]
Contract term	5 years
Zayo Canada [Member]
Segment Reporting Information [Line Items]
Number of customers that can be serviced | customer	26,000
Other [Member]
Segment Reporting Information [Line Items]
Contract term	1 year