Acquisitions and Divestitures - Additional Information (Details) $ in Millions								12 Months Ended
	Feb. 02, 2024 USD ($)	Nov. 09, 2023 USD ($) connection	Jun. 01, 2023 USD ($)	Apr. 06, 2023 USD ($) connection	Mar. 24, 2023 USD ($) connection township	May 27, 2022 USD ($) customer	Dec. 09, 2021 USD ($)	Dec. 31, 2023 USD ($) acquisition customer	Dec. 31, 2022 USD ($) acquisition	Dec. 31, 2021 USD ($)	Feb. 04, 2022 USD ($)	Jan. 01, 2022 USD ($) customer	Mar. 29, 2021 USD ($)
Business Combinations, Asset Acquisition And Divestitures [Line Items]
Consideration transferred								$ 77	$ 335
Number of acquisitions | acquisition								23	26
Assets								$ 81	$ 337
Liabilities								$ 4	6
Number of assets acquired from business combination | acquisition								5
Gain on sale of businesses								$ 0	$ 19	$ 747
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal, Statement of Income or Comprehensive Income [Extensible Enumeration]								Gain on sale of businesses	Gain on sale of businesses
Interest income								$ 73	$ 52	$ 4
Disposal Group, Disposed of by Sale | New York American Water Company, Inc.
Business Combinations, Asset Acquisition And Divestitures [Line Items]
Consideration												$ 608
Number of customers in service | customer												127,000
Disposal Group, Disposed of by Sale | Michigan American Water Company
Business Combinations, Asset Acquisition And Divestitures [Line Items]
Consideration											$ 6
Disposal Group, Disposed of by Sale | Homeowner Services Group
Business Combinations, Asset Acquisition And Divestitures [Line Items]
Consideration							$ 1,275
Gain on sale, pretax							748
Proceeds from divestiture of businesses							480
Contingent consideration receivable							75
Gain on sale of businesses									20
Interest income								50	50
Disposal Group, Disposed of by Sale | Homeowner Services Group | Secured Seller Promissory Note
Business Combinations, Asset Acquisition And Divestitures [Line Items]
Debt instrument, face amount							$ 720	$ 720
Interest rate							7.00%
Disposal Group, Disposed of by Sale | Homeowner Services Group | Secured Seller Promissory Note | Subsequent Event
Business Combinations, Asset Acquisition And Divestitures [Line Items]
Debt instrument, face amount	$ 795
Interest rate	10.00%
Debt instrument, redemption price, percentage	100.00%
Disposal Group, Disposed of by Sale | Homeowner Services Group | Secured Seller Promissory Note | Minimum
Business Combinations, Asset Acquisition And Divestitures [Line Items]
Default premium, percentage							105.50%
Disposal Group, Disposed of by Sale | Homeowner Services Group | Secured Seller Promissory Note | Maximum
Business Combinations, Asset Acquisition And Divestitures [Line Items]
Default premium, percentage							107.50%
New Jersey American Water
Business Combinations, Asset Acquisition And Divestitures [Line Items]
Consideration transferred			$ 22
Cash deposit													$ 2
Pennsylvania American Water Company
Business Combinations, Asset Acquisition And Divestitures [Line Items]
Consideration transferred		$ 230			$ 104	$ 235
Number of customers connections | connection		15,000			6,300
Number of customers in service | customer						45,000
Cash deposit						$ 20
Funded amount									$ 315
Number of townships | township					7
Pennsylvania American Water Company | Regulated Business
Business Combinations, Asset Acquisition And Divestitures [Line Items]
Assets						231
Goodwill						$ 4
Illinois American Water Company
Business Combinations, Asset Acquisition And Divestitures [Line Items]
Consideration transferred				$ 86
Number of customers connections | connection				26,000
Water and Wastewater Services
Business Combinations, Asset Acquisition And Divestitures [Line Items]
Number of customers in service | customer								18,100