INCOME TAXES - Components of Income Tax Expense (Benefit) Applicable to Pretax Earnings (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Reconciliation of Provision of Income Taxes [Line Items]
Current									$ 816	$ 891	$ 862
Deferred									620	122	371
Total income tax expense	299	463	258	417	284	356	170	202	1,436	1,013	1,233
Aflac U.S.
Reconciliation of Provision of Income Taxes [Line Items]
Current									303	533	349
Deferred									(330)	423	(167)
Total income tax expense									(27)	956	182
Aflac Japan
Reconciliation of Provision of Income Taxes [Line Items]
Current									513	358	513
Deferred									950	(301)	538
Total income tax expense									$ 1,463	$ 57	$ 1,051