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Operations and Significant Accounting Policies - Sale of U.S. Water Services (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019 USD ($)
Sale of U.S. Water Services [Abstract]
Cash Purchase Price	$ 270
Proceeds from Sale of U.S. Water Services - Net of Transaction Costs and Cash Retained	265
Approximate Gain on Sale of U.S. Water Services, After-tax	$ 10

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Approximate Gain on Sale of Affiliate, After-tax

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Approximate Proceeds from Divestiture of Business

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Cash Purchase Price for Sale of Affiliate

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Sale of U.S. Water Services [Abstract]

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