INCOME TAXES - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Jan. 01, 2015	Apr. 01, 2012
Income Taxes [Line Items]
Unrecognized tax benefit, deductibility highly certain, timing uncertain	$ 261	$ 307
Japan Tax Rate				30.80%	33.30%
Deferred tax expense (benefit)	$ 41	$ 461	$ 422
The expected U.S. tax rate	35.00%	35.00%	35.00%
Income tax expense (benefit) related to items of other comprehensive income (loss)	$ (901)	$ 1,803	$ (581)
Non-life operating loss carryforwards, limitations	only 35% of non-life operating losses can be offset against life insurance taxable income each year
Tax credit carryforward, amount	$ 0
Unrecognized tax benefits, permanent uncertainties	3
Unrecognized tax benefits, interest and penalties expense	11	11	11
Unrecognized tax benefits, accrued interest and penalties	22	30
Capital loss carryforwards	0
Expiring in 2035
Income Taxes [Line Items]
Non-life operating loss carryforwards	1
Aflac Japan
Income Taxes [Line Items]
Deferred tax expense (benefit)	42	125	299
Aflac Japan | Dollar denominated investment portfolio
Income Taxes [Line Items]
Income tax expense (benefit) related to items of other comprehensive income (loss)			$ 614
Effective income tax rate excluding income tax expense (benefit) related to Aflac Japan's dollar-denominated portfolio			31.00%
Aflac U.S.
Income Taxes [Line Items]
Deferred tax expense (benefit)	$ (1)	$ 336	$ 123