BUSINESS SEGMENT AND FOREIGN INFORMATION - Operations by Segment - Revenues (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Segment Reporting, Revenue Reconciling Item [Line Items]
Earned premiums	$ 5,643	$ 5,660	$ 5,467	$ 5,378	$ 5,324	$ 5,210	$ 4,956	$ 4,872	$ 22,148	$ 20,362	$ 18,073
Net investment income	876	869	845	882	858	843	784	794	3,473	3,280	3,007
Other income	27	32	8	25	20	17	16	30	92	81	74
Realized investment gains (losses)									(349)	(1,552)	(422)
Total revenues	6,375	6,847	5,902	6,240	5,979	5,987	5,088	5,117	25,364	22,171	20,732
Aflac Japan
Segment Reporting, Revenue Reconciling Item [Line Items]
Earned premiums									17,151	15,619	13,487
Net investment income									2,845	2,688	2,453
Other income									57	46	37
Total business segment revenues									20,053	18,353	15,977
Aflac U.S.
Segment Reporting, Revenue Reconciling Item [Line Items]
Net investment income									613	588	549
Other income									19	10	11
Total business segment revenues									5,628	5,341	5,146
Other business segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Total business segment revenues									46	54	51
Total Business Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Total business segment revenues									25,727	23,748	21,174
Corporate
Segment Reporting, Revenue Reconciling Item [Line Items]
Total revenues									262	241	217
Intercompany eliminations
Segment Reporting, Revenue Reconciling Item [Line Items]
Total revenues									(276)	(266)	(237)
Cancer [Member] | Aflac Japan
Segment Reporting, Revenue Reconciling Item [Line Items]
Earned premiums									7,537	7,541	6,852
Cancer [Member] | Aflac U.S.
Segment Reporting, Revenue Reconciling Item [Line Items]
Earned premiums									1,282	1,258	1,239
Medical And Other Health [Member] | Aflac Japan
Segment Reporting, Revenue Reconciling Item [Line Items]
Earned premiums									5,244	5,158	4,574
Life insurance | Aflac Japan
Segment Reporting, Revenue Reconciling Item [Line Items]
Earned premiums									4,370	2,920	2,061
Life insurance | Aflac U.S.
Segment Reporting, Revenue Reconciling Item [Line Items]
Earned premiums									242	230	217
Accident And Disability [Member] | Aflac U.S.
Segment Reporting, Revenue Reconciling Item [Line Items]
Earned premiums									2,213	2,194	2,104
Other Health [Member] | Aflac U.S.
Segment Reporting, Revenue Reconciling Item [Line Items]
Earned premiums									$ 1,259	$ 1,061	$ 1,026