BUSINESS SEGMENT INFORMATION - Operations by Segment - Assets (Detail) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ 133,650	$ 129,819
Aflac Japan
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	112,023	107,858
Aflac U.S.
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	19,817	19,453
Other business segments
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	338	270
Total Business Segments
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	132,178	127,581
Corporate
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	26,024	26,476
Intercompany eliminations
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ (24,552)	$ (24,238)