Acquisitions - Additional Information (Details)
Contract in Thousands
 3 Months Ended 12 Months Ended
Dec. 12, 2019
USD ($)
Nov. 20, 2019
USD ($)
Contract
Jun. 04, 2018
USD ($)
Dec. 31, 2019
USD ($)
Dec. 31, 2019
USD ($)
Acquisition
Dec. 31, 2018
USD ($)
Acquisition
Dec. 31, 2017
USD ($)
Acquisition
Business Acquisition And Divestitures [Line Items]              
Goodwill       $ 1,501,000,000 $ 1,501,000,000 $ 1,575,000,000 $ 1,379,000,000
Business Acquisitions 2019 | Regulated Water And Wastewater Systems              
Business Acquisition And Divestitures [Line Items]              
Number of companies acquired | Acquisition         21    
Purchase price         $ 235,000,000    
Purchase price allocation, assets acquired       237,000,000 237,000,000    
Contributions in aid of construction       5,000,000 $ 5,000,000    
Business Acquisitions 2019 | Regulated Businesses | Regulated Water And Wastewater Systems              
Business Acquisition And Divestitures [Line Items]              
Number of companies acquired | Acquisition         3    
Goodwill       3,000,000 $ 3,000,000    
Business Acquisition 2018 | Regulated Water And Wastewater Systems              
Business Acquisition And Divestitures [Line Items]              
Number of companies acquired | Acquisition           15  
Purchase price           $ 33,000,000  
Purchase price allocation, assets acquired           32,000,000  
Contributions in aid of construction           $ 1,000,000  
Business Acquisition 2018 | Regulated Businesses | Regulated Water And Wastewater Systems              
Business Acquisition And Divestitures [Line Items]              
Number of companies acquired | Acquisition           1  
Goodwill           $ 2,000,000  
Goodwill, expected tax deductible amount           $ 0  
Business Acquisitions 2017              
Business Acquisition And Divestitures [Line Items]              
Number of companies acquired | Acquisition             3
Business Acquisitions 2017 | Regulated Water And Wastewater Systems              
Business Acquisition And Divestitures [Line Items]              
Number of companies acquired | Acquisition             18
Purchase price             $ 210,000,000
Purchase price allocation, assets acquired             207,000,000
Contributions in aid of construction             9,000,000
Purchase price allocation, liabilities assumed             23,000,000
Debt related to purchase price allocation             7,000,000
Bargain purchase gain recognized             $ 3,000,000
Business Acquisitions 2017 | Regulated Businesses | Regulated Water And Wastewater Systems              
Business Acquisition And Divestitures [Line Items]              
Number of companies acquired | Acquisition             4
Goodwill             $ 29,000,000
Goodwill, expected tax deductible amount             $ 1,000,000
New York American Water Company              
Business Acquisition And Divestitures [Line Items]              
Purchase price   $ 608,000,000          
Number Of Customer Accounts | Contract   125          
Pivotal              
Business Acquisition And Divestitures [Line Items]              
Purchase price     $ 365,000,000        
Working capital     $ 9,000,000        
Water Solutions Holding | Discontinued Operations, Disposed of by Sale              
Business Acquisition And Divestitures [Line Items]              
Total cash consideration for business divestiture $ 31,000,000            
Pre-tax loss on business divestiture       44,000,000      
After-tax loss on business divestiture       $ 35,000,000