BUSINESS SEGMENT INFORMATION - Operations by Segment - Revenues (Details) $ in Millions		3 Months Ended
		Mar. 31, 2017 USD ($) segment	Mar. 31, 2016 USD ($)
Segment Reporting, Revenue Reconciling Item [Line Items]
Number of Reportable Insurance Business Segments | segment		2
Net earned premiums		$ 4,638	$ 4,602
Net investment income		794	801
Total revenues		5,309	5,451
Realized investment gains (losses), non-operating	[1],[2],[3],[4],[5]	(109)	40
Gain (loss) on change in fair value of derivative, interest rate component, operating		21	22
Aflac Japan
Segment Reporting, Revenue Reconciling Item [Line Items]
Net earned premiums		3,194	3,179
Net investment income, less amortized hedge costs	[2]	557	590
Other income (loss)		10	8
Total revenues		3,761	3,777
Hedge costs		52	32
Aflac U.S.
Segment Reporting, Revenue Reconciling Item [Line Items]
Net earned premiums		1,390	1,367
Other income (loss)		1	3
Net investment income		178	174
Total revenues		1,569	1,544
Other business segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Total revenues		67	65
Total Business Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Total revenues		5,397	5,386
Corporate
Segment Reporting, Revenue Reconciling Item [Line Items]
Total revenues		87	67
Intercompany eliminations
Segment Reporting, Revenue Reconciling Item [Line Items]
Total revenues		$ (66)	$ (42)

[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