Other Intangible Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Other Intangible Assets [Line Items]
Intangible Assets, Gross	$ 48.0	$ 40.8
Accumulated Amortization	(20.7)	(19.4)
Intangible assets, net	27.3	21.4
Amortization expense for 2016	1.3
Amortization expense for 2017	1.3
Amortization expense for 2018	0.2
Rights-of-Way [Member]
Other Intangible Assets [Line Items]
Indefinite-lived intangible assets	17.3	$ 17.3
Line space history [Member]
Other Intangible Assets [Line Items]
Indefinite-lived intangible assets	$ 7.2
Supply contracts [Member]
Other Intangible Assets [Line Items]
Estimated useful life (years)	11 years 6 months	11 years 6 months
Intangible Assets, Gross	$ 12.2	$ 12.2
Accumulated Amortization	(10.0)	(8.9)
Intangible assets, net	$ 2.2	$ 3.3
Trademarks [Member]
Other Intangible Assets [Line Items]
Estimated useful life (years)	4 years	4 years
Intangible Assets, Gross	$ 0.7	$ 0.7
Accumulated Amortization	(0.7)	(0.7)
Intangible assets, net	0.0	0.0
Noncompete Agreements [Member]
Other Intangible Assets [Line Items]
Intangible Assets, Gross	1.3	1.3
Accumulated Amortization	(1.3)	(1.3)
Intangible assets, net	$ 0.0	$ 0.0
Capacity contract [Member]
Other Intangible Assets [Line Items]
Estimated useful life (years)	8 years	8 years
Intangible Assets, Gross	$ 9.3	$ 9.3
Accumulated Amortization	(8.7)	(8.5)
Intangible assets, net	$ 0.6	$ 0.8
Minimum [Member]
Other Intangible Assets [Line Items]
Estimated useful life (years)	3 years
Minimum [Member] | Noncompete Agreements [Member]
Other Intangible Assets [Line Items]
Estimated useful life (years)	3 years	3 years
Maximum [Member]
Other Intangible Assets [Line Items]
Estimated useful life (years)	11 years 6 months
Maximum [Member] | Noncompete Agreements [Member]
Other Intangible Assets [Line Items]
Estimated useful life (years)	10 years	10 years
Depreciation and amortization [Member]
Other Intangible Assets [Line Items]
Amortization of Intangible Assets	$ 1.3	$ 1.3	$ 4.3