Note 12 - Goodwill and Other Intangible Assets - Identifiable Intangible Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Finite-lived intangible assets, gross	$ 86.0	$ 10.5
Less accumulated amortization	(12.3)	(8.1)
Total identifiable intangible assets, net	73.7	2.4
Noncompete Agreements [Member]
Finite-lived intangible assets, gross	$ 0.2
Weighted average amortization period (Year)	5 years
Customer Relationships [Member]
Finite-lived intangible assets, gross	$ 75.3
Weighted average amortization period (Year)	10 years
LDC Network Access [Member]
Finite-lived intangible assets, gross	$ 10.5	$ 10.5
Weighted average amortization period (Year)	10 years