SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended				12 Months Ended								12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009 Accounting Standards Update 2010-26	Dec. 31, 2012 Aflac Japan	Dec. 31, 2011 Aflac Japan	Dec. 31, 2010 Aflac Japan	Dec. 31, 2012 Retained earnings:	Dec. 31, 2011 Retained earnings:	Dec. 31, 2010 Retained earnings:	Dec. 31, 2009 Retained earnings: Accounting Standards Update 2010-26	Dec. 31, 2009 Accumulated Other Comprehensive Income (Loss) Accounting Standards Update 2010-26	Dec. 31, 2012 Dollar denominated investment portfolio Aflac Japan	Dec. 31, 2011 Dollar denominated investment portfolio Aflac Japan	Dec. 31, 2010 Dollar denominated investment portfolio Aflac Japan
Significant Accounting Policies [Line Items]
Aflac Japan's percentage of the Company's total revenues					77.00%	75.00%	75.00%
Aflac Japan's percentage of the Company's total assets					87.00%	87.00%
Income tax expense (benefit) related to items of other comprehensive income (loss)	$ 1,078	$ 392	$ (32)										$ 492	$ (152)	$ (322)
Effective income tax rate excluding income tax expense (benefit) related to Aflac Japan's dollar-denominated portfolio													32.00%	34.00%	32.00%
Cumulative effect of change in accounting principle, net of income taxes				$ (458)				$ 0	$ 0	$ (25)	$ (391)	$ (67)