Segment Reporting (Summary of Financial Information by Segments) (Details) - USD ($) $ in Millions	3 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Jun. 30, 2016
Segment Reporting Information [Line Items]
Revenue from external customers	$ 504.9	$ 366.8
Segment Adjusted EBITDA	260.6	215.4
Total assets	6,834.0	6,165.9	$ 6,727.5
Capital expenditures	208.3	159.2
Dark Fiber Solutions [Member]
Segment Reporting Information [Line Items]
Revenue from external customers	148.4	135.0
Segment Adjusted EBITDA	108.2	96.6
Total assets	3,237.8	2,862.9	3,155.0
Capital expenditures	128.1	93.5
Network Connectivity [Member]
Segment Reporting Information [Line Items]
Revenue from external customers	175.6	167.0
Segment Adjusted EBITDA	91.6	88.7
Total assets	1,898.1	1,825.5	1,901.8
Capital expenditures	48.9	46.7
Colocation and Cloud Infrastructure [Member]
Segment Reporting Information [Line Items]
Revenue from external customers	64.1	58.3
Segment Adjusted EBITDA	32.2	28.4
Total assets	1,090.5	1,022.1	1,069.4
Capital expenditures	28.0	19.0
Zayo Canada [Member]
Segment Reporting Information [Line Items]
Revenue from external customers	112.2
Segment Adjusted EBITDA	27.5
Total assets	475.7		477.6
Capital expenditures	3.3
Other [Member]
Segment Reporting Information [Line Items]
Revenue from external customers	4.6	6.5
Segment Adjusted EBITDA	1.1	1.7
Total assets	32.3	36.3	33.4
Corporate/Eliminations [Member]
Segment Reporting Information [Line Items]
Total assets	$ 99.6	$ 419.1	$ 90.3