BUSINESS SEGMENT INFORMATION - Operations by Segment - Pretax Earnings (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2016	Mar. 31, 2015
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Pretax operating earnings		$ 1,109	$ 1,035
Realized investment gains (losses), non-operating	[1]	51	(4)
Other non-operating income (loss)		(43)	(18)
Earnings before income taxes		1,117	1,013
Income taxes applicable to pretax operating earnings		383	357
Effect of foreign currency translation on operating earnings		13	(58)
Gain (loss) on change in fair value of derivative, interest rate component, operating		22	17
Gain (Loss) on Investments		73	13
Aflac Japan
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Pretax operating earnings		838	819
Aflac U.S.
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Pretax operating earnings		332	285
Other business segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Pretax operating earnings		3	1
Total Business Segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Pretax operating earnings		1,173	1,105
Interest expense, noninsurance operations
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Pretax operating earnings		(29)	(49)
Corporate and eliminations
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Pretax operating earnings		$ (35)	$ (21)

[1] Excluding a gain of $22 and $17 for the three-month periods ended March 31, 2016, and 2015, respectively, related to the interest rate component of the change in fair value of foreign currency swaps on notes payable which is classified as an operating gain when analyzing segment operations