Segment Reporting (Summary of Financial Information by Segments) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016	Jun. 30, 2016
Segment Reporting Information [Line Items]
Revenue from external customers	$ 550.2	$ 478.0	$ 1,561.8	$ 1,214.4
Segment Adjusted EBITDA	282.0	242.8	806.0	677.1
Total assets	8,548.4		8,548.4		$ 6,727.5
Capital expenditures	208.3	185.1	630.2	516.7
Fiber Solutions [Member]
Segment Reporting Information [Line Items]
Revenue from external customers	179.6	169.4	531.2	476.6
Segment Adjusted EBITDA	137.6	131.3	416.8	364.2
Total assets	4,319.7		4,319.7		3,780.9
Capital expenditures	119.9	111.0	381.6	315.1
Transport [Member]
Segment Reporting Information [Line Items]
Revenue from external customers	110.5	102.6	323.0	284.4
Segment Adjusted EBITDA	45.7	42.5	134.9	122.6
Total assets	1,252.3		1,252.3		964.8
Capital expenditures	40.2	30.3	111.1	90.1
Enterprise Networks [Member]
Segment Reporting Information [Line Items]
Revenue from external customers	121.7	105.3	350.8	244.4
Segment Adjusted EBITDA	46.6	37.4	126.9	105.8
Total assets	1,180.0		1,180.0		849.2
Capital expenditures	22.6	24.3	63.6	63.7
zColo [Member]
Segment Reporting Information [Line Items]
Revenue from external customers	53.6	47.9	157.3	145.0
Segment Adjusted EBITDA	28.7	24.2	82.6	74.5
Total assets	931.0		931.0		884.3
Capital expenditures	23.7	17.2	69.9	45.5
Allstream
Segment Reporting Information [Line Items]
Revenue from external customers	79.3	48.0	185.4	48.0
Segment Adjusted EBITDA	22.0	6.1	41.3	6.1
Total assets	644.8		644.8		72.6
Capital expenditures	1.9	2.3	4.0	2.3
Other [Member]
Segment Reporting Information [Line Items]
Revenue from external customers	5.5	4.8	14.1	16.0
Segment Adjusted EBITDA	1.4	$ 1.3	3.5	$ 3.9
Total assets	31.5		31.5		33.5
Corp/Eliminations [Member]
Segment Reporting Information [Line Items]
Total assets	$ 189.1		$ 189.1		$ 142.2