BUSINESS SEGMENT INFORMATION - Operations by Segment - Revenues (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013 segment	Mar. 31, 2012
Segment Reporting, Revenue Reconciling Item [Line Items]
Number of Reportable Insurance Business Segments	2
Earned premiums	$ 5,184	$ 5,378
Net investment income	833	882
Other income	35	25
Realized investment gains (losses)	156	(45)
Total revenues	6,208	6,240
Aflac Japan
Segment Reporting, Revenue Reconciling Item [Line Items]
Earned premiums	3,905	4,148
Net investment income	674	730
Other income	26	16
Total business segment revenues	4,605	4,894
Aflac U.S.
Segment Reporting, Revenue Reconciling Item [Line Items]
Earned premiums	1,280	1,231
Net investment income	157	152
Other income	1	2
Total business segment revenues	1,438	1,385
Other business segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Total business segment revenues	12	14
Total Business Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Total business segment revenues	6,055	6,293
Corporate
Segment Reporting, Revenue Reconciling Item [Line Items]
Total revenues	92	68
Intercompany eliminations
Segment Reporting, Revenue Reconciling Item [Line Items]
Total revenues	$ (95)	$ (76)