Note 12 - Goodwill and Other Intangible Assets - Identifiable Intangible Assets (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Finite-lived intangible assets, gross	$ 151.5	$ 86.0
Less accumulated amortization	(23.1)	(20.9)
Total identifiable intangible assets, net	128.4	65.1
Noncompete Agreements [Member]
Finite-lived intangible assets, gross	$ 1.2	0.2
Weighted average amortization period (Year)	6 years 255 days
Customer Relationships [Member]
Finite-lived intangible assets, gross	$ 139.8	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