Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2017	Oct. 25, 2017
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2017
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	Q3
Trading Symbol	AFL
Entity Registrant Name	AFLAC INC
Entity Central Index Key	0000004977
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		393,149,620