Segment Reporting (Narrative) (Details)	3 Months Ended
	Sep. 30, 2017 customer segment item
Segment Reporting Information [Line Items]
Number of segments | segment	6
Fiber Solutions [Member] | Minimum
Segment Reporting Information [Line Items]
Number of dark fiber pairs leased to customers	2
Contract term	3 years
Fiber Solutions [Member] | Maximum
Segment Reporting Information [Line Items]
Number of dark fiber pairs leased to customers	12
Contract term	20 years
Transport [Member] | Minimum
Segment Reporting Information [Line Items]
Contract term	2 years
Transport [Member] | Maximum
Segment Reporting Information [Line Items]
Contract term	5 years
zColo [Member] | Minimum
Segment Reporting Information [Line Items]
Contract term	2 years
zColo [Member] | Maximum
Segment Reporting Information [Line Items]
Contract term	5 years
Allstream
Segment Reporting Information [Line Items]
Number of customers that can be serviced | customer	70,000
Other [Member]
Segment Reporting Information [Line Items]
Contract term	1 year