INCOME TAXES - Income Tax Effects of Temporary Differences that Gave Rise to Deferred Income Tax Assets and Liabilities (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Deferred income tax liabilities:
Deferred policy acquisition costs	$ 2,731	$ 2,799
Unrealized gains on investment securities	1,522	397
Policyholder protection corporation obligation	10	0
Difference in tax basis of investment in Aflac Japan	288	0
Premiums receivable	164	153
Policy benefit reserves	1,995	1,896
Total deferred income tax liabilities	6,710	5,245
Deferred income tax assets:
Depreciation	124	134
Policyholder protection corporation obligation	0	5
Difference in tax basis of investment in Aflac Japan	0	47
Other basis differences in investment securities	1,471	1,363
Unfunded retirement benefits	45	44
Other accrued expenses	60	64
Policy and contract claims	67	106
Unrealized exchange loss on yen-denominated notes payable	36	124
Deferred compensation	203	201
Capital loss carryforwards	716	784
Other	438	405
Total deferred income tax assets	3,160	3,277
Net deferred income tax liability	3,550	1,968
Current income tax liability	308	340
Total income tax liability	$ 3,858	$ 2,308