Operations and Significant Accounting Policies - Sale of U.S. Water Services (Details) $ in Millions	6 Months Ended
	Jun. 30, 2019 USD ($)
Business Segments [Line Items]
Approximate Gain on Sale of U.S. Water Services, After-tax	$ 11.1
U.S. Water Services [Member]
Business Segments [Line Items]
Cash Purchase Price	270.0
Proceeds from Sale of U.S. Water Services - Net of Transaction Costs and Cash Retained	265.0
Approximate Gain on Sale of U.S. Water Services, After-tax	$ 11.1