Income Taxes - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended																								12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009		Dec. 31, 2011 Expiring in 2029	Dec. 31, 2011 Expiring in 2030	Dec. 31, 2011 Expire in Twenty Thirty One	Dec. 31, 2011 Expiring in 2013	Dec. 31, 2011 Expiring in 2014	Dec. 31, 2011 Expiring in 2015	Dec. 31, 2011 Expiring In Twenty Sixteen	Dec. 31, 2011 Expired In Twenty Eleven	Dec. 31, 2011 Aflac Japan	Dec. 31, 2010 Aflac Japan	Dec. 31, 2009 Aflac Japan	Dec. 31, 2011 Aflac Japan Loss of foreign tax credits	Dec. 31, 2011 Aflac U.S.	Dec. 31, 2010 Aflac U.S.	Dec. 31, 2009 Aflac U.S.	Dec. 31, 2011 Aflac U.S. Loss of foreign tax credits	Apr. 01, 2015 Change in Income Tax Rate	Apr. 01, 2012 Change in Income Tax Rate	Dec. 31, 2011 Aflac Japan Dollar-denominated investment portfolio	Dec. 31, 2010 Aflac Japan Dollar-denominated investment portfolio	Dec. 31, 2009 Aflac Japan Dollar-denominated investment portfolio
Income Taxes [Line Items]
Japan tax rate																							30.80%	33.30%
Deferred taxes	$ 137		$ 379		$ (92)										$ (290)	$ 546	$ 62	$ (744)	$ 427	$ (167)	$ (154)	$ 744
Temporary difference effect of Japan tax rate change	744
The expected U.S. tax rate	35.00%
Income tax expense (benefit) related to items of other comprehensive income (loss)	392		(32)		351																				(152)	(322)	12
Effective income tax rate excluding income tax expense (benefit) related to Aflac Japan's dollar-denominated portfolio																									34.00%	31.00%	35.00%
Non-life operating loss carryforwards, limitations	only 35% of non-life operating losses can be offset against life insurance taxable income each year.
Non-life operating loss carryforwards							17	39	34
Non-life operating loss carryforwards, expiration year							2029	2030	2031
Capital loss carryforwards available to offset capital gains	2,240									214	299	550	1,177	7
Capital loss carryforwards, expiration year										2013	2014	2015	2016	2011
Unrecognized tax benefits, tax positions for which the ultimate deductibility is highly certain	31	[1]	24	[1]	17	[1]
Unrecognized tax benefits, permanent uncertainties	2
Unrecognized tax benefits, interest and penalties expense	5		3		1
Unrecognized tax benefits, accrued interest and penalties	$ 19		$ 14

[1] Amounts do not include tax deductions of $10 at December 31, 2011, $8 at December 31, 2010, and $6 at January 1, 2010.