Commitments and Contingencies Legal Proceedings and Settlements (Details) $ in Millions	3 Months Ended
	Mar. 31, 2016 USD ($) defendant	Dec. 31, 2015 USD ($)
Regulatory Matters [Abstract]
Customer Refund Liability, Current	$ 16.6	$ 16.3
Rate Case Incremental Revenues	$ 8.9
Southeast Louisiana Flood Protection Litigation
Loss Contingencies [Line Items]
Loss Contingency, Number of Defendants (in ones) | defendant	100