Operations by Segment - Assets (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ 117,102	$ 101,039
Aflac Japan
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	102,323	87,061
Aflac U.S.
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	14,177	13,095
Other business segments
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	160	155
Total Business Segments
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	116,660	100,311
Corporate
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	16,741	14,047
Intercompany eliminations
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ (16,299)	$ (13,319)