BUSINESS SEGMENT INFORMATION - Operations by Segment - Assets (Detail) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ 144,101	$ 118,256
Aflac Japan
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	121,677	97,646
Aflac U.S.
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	20,126	18,537
Other business segments
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	270	188
Total Business Segments
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	142,073	116,371
Corporate
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	29,617	23,375
Intercompany eliminations
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ (27,589)	$ (21,490)