BUSINESS SEGMENT INFORMATION - Operations by Segment - Revenues (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013 segment	Jun. 30, 2012
Segment Reporting, Revenue Reconciling Item [Line Items]
Number of Reportable Insurance Business Segments			2
Earned premiums	$ 5,013	$ 5,467	$ 10,197	$ 10,845
Net investment income	813	845	1,646	1,728
Other income	17	8	52	32
Realized investment gains (losses)	201	(418)	357	(463)
Total revenues	6,044	5,902	12,252	12,142
Aflac Japan
Segment Reporting, Revenue Reconciling Item [Line Items]
Earned premiums	3,717	4,216	7,622	8,364
Net investment income	653	691	1,327	1,421
Other income	12	0	38	16
Total revenues	4,382	4,907	8,987	9,801
Aflac U.S.
Segment Reporting, Revenue Reconciling Item [Line Items]
Earned premiums	1,295	1,251	2,575	2,482
Net investment income	158	153	314	304
Other income	1	2	4	5
Total revenues	1,454	1,406	2,893	2,791
Other business segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Total revenues	14	10	26	24
Total Business Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Total revenues	5,850	6,323	11,906	12,616
Corporate
Segment Reporting, Revenue Reconciling Item [Line Items]
Total revenues	66	64	159	128
Intercompany eliminations
Segment Reporting, Revenue Reconciling Item [Line Items]
Total revenues	$ (73)	$ (67)	$ (170)	$ (139)