Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2019	Nov. 08, 2019
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q3
Entity Registrant Name	AMERICAN PUBLIC EDUCATION INC
Entity Central Index Key	0001201792
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Emerging Filing Entity	false
Entity Small Business	false
Entity Shell Company	false
Entity Current Reporting Status	Yes
Entity Common Stock, Shares Outstanding		15,398,238