Document and Entity Information	3 Months Ended
	Mar. 31, 2014	May 01, 2014
Document And Entity Information [Line Items]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2014
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	Q1
Trading Symbol	AWK
Entity Registrant Name	American Water Works Company, Inc.
Entity Central Index Key	0001410636
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		179,018,709