Acquisitions (Narrative) (Details) € in Millions, CAD in Millions, $ in Millions						3 Months Ended
	Apr. 01, 2016 USD ($) ft² item	Jan. 15, 2016 CAD building item mi	Jan. 15, 2016 USD ($) building item mi	Dec. 31, 2015 EUR (€) ft²	Dec. 31, 2015 USD ($) ft²	Sep. 30, 2016 CAD item	Sep. 30, 2016 EUR (€) item	Sep. 30, 2016 USD ($) item	Jan. 15, 2016 USD ($)
Business Acquisition [Line Items]
Number of business combinations completed | item						38	38	38
Acquisition related costs								$ 3.0
Clearview
Business Acquisition [Line Items]
Business acquisition, percentage of voting interests acquired	100.00%
Net consideration paid	$ 18.3
Purchase price, held in escrow	$ 1.7
Number of data centers acquired | item	2
Acquired facility size (in square feet) | ft²	30,000
Allstream
Business Acquisition [Line Items]
Business acquisition, percentage of voting interests acquired		100.00%							100.00%
Net consideration paid		CAD 422.9	$ 297.6
Purchase price, held in escrow		4.2	$ 3.2
Working capital and other liabilities assumed in the acquisition		CAD 42.1							$ 29.6
Additional Route Miles Acquired | mi		18,000	18,000
Long-Haul Fiber Network Acquired | mi		12,500	12,500
Metro Fiber Network Acquired | mi		5,500	5,500
Network concentrating net buildings | building		3,300	3,300
Number of metropolitan markets | item		5	5
Other post retirement benefits plan liability assumed		CAD 12.8	$ 8.3			CAD 13.0		9.9
Viatel
Business Acquisition [Line Items]
Business acquisition, percentage of voting interests acquired				100.00%	100.00%
Net consideration paid				€ 92.9	$ 101.2
Refund of escrow reflected as a cash inflow from investing activitie							€ 1.3	$ 1.5
Dallas Data Center
Business Acquisition [Line Items]
Net consideration paid					$ 16.6
Acquired facility size (in square feet) | ft²				36,000	36,000