Operations and Significant Accounting Policies - Sale of U.S. Water Services (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2019
Business Segments [Line Items]
Proceeds from Sale of U.S. Water Services - Net of Transaction Costs and Cash Retained		$ 270.0
Gain on Sale of U.S. Water Services, After-tax	$ 9.9	$ 13.2