BUSINESS SEGMENT INFORMATION - Operations by Segment - Pretax Earnings (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Pretax operating earnings		$ 1,027	$ 1,077
Realized investment gains (losses), non-operating	[1],[2],[3],[4],[5]	(109)	40
Other non-operating income (loss)	[4]	(20)	0
Earnings before income taxes		898	1,117
Income taxes applicable to pretax operating earnings		351	372
Effect of foreign currency translation on operating earnings		5	13
Gain (loss) on change in fair value of derivative, interest rate component, operating		21	22
Aflac Japan
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Pretax operating earnings	[3]	769	806
Hedge costs		52	32
Aflac U.S.
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Pretax operating earnings		310	332
Other business segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Pretax operating earnings		0	3
Total Business Segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Pretax operating earnings		1,079	1,141
Interest expense, noninsurance operations
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Pretax operating earnings		(29)	(29)
Corporate and eliminations
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Pretax operating earnings		$ (23)	$ (35)

[1] Excluding a gain of $21 and $22 for the three-month periods ended March 31, 2017, and 2016, 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

[2] Hedge costs related to hedging U.S. dollar-denominated investments held in Aflac Japan were $52 and $32 for the three-month periods ended March 31, 2017, and 2016, respectively, and have been reclassified from realized investment gains (losses) and reported as a deduction from net investment income when analyzing segment operations to conform to current year reporting.

[3] Hedge costs related to hedging U.S. dollar-denominated investments held in Aflac Japan were $52 and $32 for the three-month periods ended March 31, 2017, and 2016, respectively, and have been reclassified from realized investment gains (losses) and reported as a deduction from pretax operating earnings when analyzing segment operations to conform to current year reporting.

[4] Prior year foreign currency transaction gains and losses have been reclassified from other non-operating income (loss) to realized investment gains (losses) to conform to current-year reporting classifications. These reclassifications had no impact on total earnings before income taxes.

[5] Prior year foreign currency transaction gains and losses have been reclassified from other non-operating income (loss) to realized investment gains (losses) to conform to current-year reporting classifications. These reclassifications had no impact on total revenues