Revenue Recognition - Disaggregated Revenues (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	$ 1,003	$ 925
Other revenues not from contracts with customers	8	13
Operating revenues	1,011	938
Other
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	83	78
Operating revenues	83	78
Regulated Businesses | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	920	847
Alternative revenue programs	2	9
Lease contract revenue	2	2
Other revenues not from contracts with customers	8	13
Operating revenues	928	860
Regulated Businesses | Water Services | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	826	763
Other revenues not from contracts with customers	4	2
Operating revenues	830	765
Regulated Businesses | Wastewater Services | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	85	76
Operating revenues	85	76
Regulated Businesses | Miscellaneous Utility Charge | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	9	8
Operating revenues	9	8
Regulated Businesses | Residential | Water Services | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	502	460
Other revenues not from contracts with customers	2	1
Operating revenues	504	461
Regulated Businesses | Residential | Wastewater Services | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	59	54
Operating revenues	59	54
Regulated Businesses | Commercial | Water Services | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	186	170
Other revenues not from contracts with customers	1	1
Operating revenues	187	171
Regulated Businesses | Commercial | Wastewater Services | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	16	14
Operating revenues	16	14
Regulated Businesses | Fire service | Water Services | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	41	39
Operating revenues	41	39
Regulated Businesses | Industrial | Water Services | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	42	38
Operating revenues	42	38
Regulated Businesses | Industrial | Wastewater Services | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	2	2
Operating revenues	2	2
Regulated Businesses | Public and other | Water Services | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	55	56
Other revenues not from contracts with customers	1
Operating revenues	56	56
Regulated Businesses | Public and other | Wastewater Services | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	8	6
Operating revenues	$ 8	$ 6