BUSINESS SEGMENT INFORMATION - Operations by Segment - Assets (Detail) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ 117,455	$ 119,767
Aflac Japan
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	97,158	98,525
Aflac U.S.
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	18,687	18,383
Other business segments
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	176	128
Total Business Segments
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	116,021	117,036
Corporate
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	22,676	24,636
Intercompany eliminations
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ (21,242)	$ (21,905)