SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended					3 Months Ended		9 Months Ended		1 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011 Aflac Japan	Sep. 30, 2010 Aflac Japan	Dec. 31, 2010 Aflac Japan	Sep. 30, 2011 Aflac Japan Dollar-denominated investment portfolio	Sep. 30, 2010 Aflac Japan Dollar-denominated investment portfolio	Sep. 30, 2011 Aflac Japan Dollar-denominated investment portfolio	Sep. 30, 2010 Aflac Japan Dollar-denominated investment portfolio	Jan. 31, 2012 New Accounting Pronouncement, Effect Accounting Standards Update 2010-26 Lower Limit	Jan. 31, 2012 New Accounting Pronouncement, Effect Accounting Standards Update 2010-26 Upper Limit
Significant Accounting Policies [Line Items]
Aflac Japan's percentage of the Company's total revenues					75.00%	75.00%
Aflac Japan's percentage of the Company's total assets					87.00%		86.00%
Income tax expense (benefit) related to items of other comprehensive income (loss)	$ (214)	$ 112	$ 87	$ 343				$ 186	$ 143	$ 236	$ 238
Effective income tax rate excluding income tax expense (benefit) related to Aflac Japan's dollar-denominated portfolio								36.60%	33.00%	35.60%	33.30%
Estimated adjustment to the opening balance of retained earnings upon adoption of new accounting guidance												$ 500	$ 700
Estimated adjustment to the opening balance of retained earnings upon adoption of new accounting guidance, percentage of equity												4.50%	6.30%