BUSINESS SEGMENT INFORMATION - Operations by Segment - Revenues and Pretax Earnings (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012 segment	Mar. 31, 2011
Segment Reporting, Revenue Reconciling Item [Line Items]
Reportable insurance business segments	2
Earned premiums	$ 5,378	$ 4,872
Net investment income	882	794
Other income	25	30
Total business segment revenues	6,293	5,702
Realized investment gains (losses)	(45)	(579)
Total revenues	6,240	5,117
Pretax operating earnings	1,247	1,170
Earnings before income taxes	1,202	591
Income taxes applicable to pretax operating earnings	433	405
Effect of foreign currency translation on operating earnings	20	49
Aflac Japan
Segment Reporting, Revenue Reconciling Item [Line Items]
Earned premiums	4,148	3,702
Net investment income	730	649
Other income	16	20
Total business segment revenues	4,894	4,371
Pretax operating earnings	1,040	974
Aflac U.S.
Segment Reporting, Revenue Reconciling Item [Line Items]
Earned premiums	1,231	1,169
Net investment income	152	144
Other income	2	3
Total business segment revenues	1,385	1,316
Pretax operating earnings	271	251
Other business segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Total business segment revenues	14	15
Pretax operating earnings	0	0
Total Business Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Pretax operating earnings	1,311	1,225
Corporate
Segment Reporting, Revenue Reconciling Item [Line Items]
Total revenues	68	61
Intercompany eliminations
Segment Reporting, Revenue Reconciling Item [Line Items]
Total revenues	(76)	(67)
Interest expense, noninsurance operations
Segment Reporting, Revenue Reconciling Item [Line Items]
Pretax operating earnings	(44)	(41)
Corporate and eliminations
Segment Reporting, Revenue Reconciling Item [Line Items]
Pretax operating earnings	$ (20)	$ (14)