BUSINESS SEGMENT INFORMATION - Operations by Segment - Assets (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ 120,538	$ 131,094
Aflac Japan
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	103,098	113,678
Aflac U.S.
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	16,130	16,122
Other business segments
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	152	154
Total Business Segments
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	119,380	129,954
Corporate
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	19,861	20,318
Intercompany eliminations
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ (18,703)	$ (19,178)