INCOME TAXES - Additional Information (Detail) - USD ($) $ in Millions	1 Months Ended	3 Months Ended	12 Months Ended
	Jan. 31, 2018	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 22, 2017
Income Taxes [Line Items]
Japan Tax Rate		28.20%	28.20%	28.80%	30.80%
U.S. federal statutory corporate income tax rate			35.00%	35.00%	35.00%
Deferred Tax Assets, Gross		$ 5,916	$ 5,916	$ 5,498
Deferred Tax Liabilities, Gross		9,828	9,828	10,554
Deferred Tax Liabilities, Net		4,569	4,569	5,056
Income Tax Expense, Gross, Continuing Operations, Adjustment of Deferred Tax Assets		1,000
Income Tax Benefit, Gross, Continuing Operations, Adjustment of Deferred Tax Liabilities		2,900
Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability		1,900
Deferred Tax Assets, Valuation Allowance		(657)	(657)	0
Unrecognized tax benefit, deductibility highly certain, timing uncertain		13	$ 13	293
Non-life operating loss carryforwards, limitations			only 35% of non-life operating losses can be offset against life insurance taxable income each year
Unrecognized tax benefits, permanent uncertainties		1	$ 1
Unrecognized tax benefits, interest and penalties expense			1	13	$ 11
Unrecognized tax benefits, accrued interest and penalties		2	2	$ 26
Capital loss carryforwards		$ 0	$ 0
Aflac Japan
Income Taxes [Line Items]
Deferred Tax Liabilities, Net						$ 4,500
Pre Tax Reform
Income Taxes [Line Items]
Deferred Tax Assets, Gross						6,200
Deferred Tax Liabilities, Gross						12,700
Deferred Tax Liabilities, Net						$ 6,500
Subsequent Event
Income Taxes [Line Items]
U.S. federal statutory corporate income tax rate	21.00%