INCOME TAXES (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended			12 Months Ended
	Jan. 31, 2018	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2017	Dec. 22, 2017
Income Taxes [Line Items]
Effective tax rate	21.00%	21.00%		35.00%	35.00%
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)		(1,900)
Deferred Tax Assets, Valuation Allowance			$ 700		$ 700
Aflac Japan
Income Taxes [Line Items]
Deferred Tax Liabilities, Net						$ 4,500