BUSINESS SEGMENT INFORMATION - Operations by Segment - Revenues (Details) $ in Millions		3 Months Ended
		Mar. 31, 2016 USD ($) segment	Mar. 31, 2015 USD ($)
Segment Reporting, Revenue Reconciling Item [Line Items]
Number of Reportable Insurance Business Segments | segment		2
Net earned premiums		$ 4,602	$ 4,432
Net investment income		801	782
Total revenues		5,451	5,226
Other non-operating income (loss)		(43)	(18)
Realized investment gains (losses), non-operating	[1]	51	(4)
Gain (loss) on change in fair value of derivative, interest rate component, operating		22	17
Aflac Japan
Segment Reporting, Revenue Reconciling Item [Line Items]
Net earned premiums		3,179	3,078
Net investment income		622	613
Other income (loss)		8	8
Total revenues		3,809	3,699
Aflac U.S.
Segment Reporting, Revenue Reconciling Item [Line Items]
Net earned premiums		1,367	1,339
Net investment income		174	166
Other income (loss)		3	3
Total revenues		1,544	1,508
Other business segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Total revenues		65	26
Total Business Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Total revenues		5,418	5,233
Corporate
Segment Reporting, Revenue Reconciling Item [Line Items]
Total revenues		67	97
Intercompany eliminations
Segment Reporting, Revenue Reconciling Item [Line Items]
Total revenues		$ (42)	$ (82)

[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