v3.25.1
Cover Page - shares
3 Months Ended
Mar. 31, 2025
Apr. 21, 2025
Cover [Abstract]    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Mar. 31, 2025  
Document Transition Report false  
Entity File Number 001-34028  
Entity Registrant Name AMERICAN WATER WORKS COMPANY, INC.  
Entity Incorporation, State or Country Code DE  
Entity Tax Identification Number 51-0063696  
Entity Address, Address Line One 1 Water Street  
Entity Address, City or Town Camden  
Entity Address, State or Province NJ  
Entity Address, Postal Zip Code 08102-1658  
City Area Code 856  
Local Phone Number 955-4001  
Title of 12(b) Security Common stock, par value $0.01 per share  
Trading Symbol AWK  
Security Exchange Name NYSE  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Large Accelerated Filer  
Entity Small Business false  
Entity Emerging Growth Company false  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding   195,011,615
Amendment Flag false  
Document Fiscal Year Focus 2025  
Document Fiscal Period Focus Q1  
Entity Central Index Key 0001410636  
Current Fiscal Year End Date --12-31