BUSINESS SEGMENT INFORMATION - Operations by Segment - Revenues and Pretax Earnings (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012 segment	Jun. 30, 2011	Jun. 30, 2012 segment	Jun. 30, 2011
Segment Reporting, Revenue Reconciling Item [Line Items]
Reportable insurance business segments	2		2
Earned premiums	$ 5,467	$ 4,956	$ 10,845	$ 9,828
Net investment income	845	784	1,728	1,579
Other income	8	16	32	44
Realized investment gains (losses)	(418)	(668)	(463)	(1,247)
Total revenues	5,902	5,088	12,142	10,204
Pretax operating earnings	1,159	1,112	2,406	2,283
Earnings before income taxes	741	444	1,943	1,036
Income taxes applicable to pretax operating earnings	404	384	837	789
Effect of foreign currency translation on operating earnings	6	51	26	99
Aflac Japan
Segment Reporting, Revenue Reconciling Item [Line Items]
Earned premiums	4,216	3,770	8,364	7,472
Net investment income	691	636	1,421	1,285
Other income	0	5	16	25
Total business segment revenues	4,907	4,411	9,801	8,782
Pretax operating earnings	964	925	2,004	1,899
Aflac U.S.
Segment Reporting, Revenue Reconciling Item [Line Items]
Earned premiums	1,251	1,186	2,482	2,356
Net investment income	153	148	304	291
Other income	2	3	5	6
Total business segment revenues	1,406	1,337	2,791	2,653
Pretax operating earnings	258	243	529	494
Other business segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Total business segment revenues	10	13	24	28
Total Business Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Total business segment revenues	6,323	5,761	12,616	11,463
Pretax operating earnings	1,222	1,168	2,533	2,393
Corporate
Segment Reporting, Revenue Reconciling Item [Line Items]
Total revenues	64	60	128	121
Interest expense, noninsurance operations
Segment Reporting, Revenue Reconciling Item [Line Items]
Pretax operating earnings	(45)	(41)	(89)	(82)
Corporate and eliminations
Segment Reporting, Revenue Reconciling Item [Line Items]
Pretax operating earnings	(18)	(15)	(38)	(28)
Intercompany eliminations
Segment Reporting, Revenue Reconciling Item [Line Items]
Total revenues	$ (67)	$ (65)	$ (139)	$ (133)