BUSINESS SEGMENT INFORMATION - Operations by Segment - Assets (Detail) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ 135,394	$ 129,819
Aflac Japan
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	113,497	107,858
Aflac U.S.
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	19,996	19,453
Other business segments
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	471	270
Total Business Segments
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	133,964	127,581
Corporate and eliminations
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ 1,430	$ 2,238