Commitments and Contingencies (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)
Commitments and Contingencies Disclosure [Abstract]
Operating Leases, Rent Expense	$ 4.1	$ 2.4	$ 10.8	$ 7.4
Jointly Owned Utility Plant Aggregate Construction Cost	235.0		$ 235.0
Jointly Owned Utility Plant Amount Paid For Cable Build	$ 1.7
Up-Front Payments for Services, Upper Range, Years	25		25
Proceeds From Sale of Capacity	$ 23.5		$ 23.5