BUSINESS SEGMENT INFORMATION - Operations by Segment - Revenues (Details) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2015 USD ($)	Jun. 30, 2014 USD ($)	Jun. 30, 2015 USD ($) segment	Jun. 30, 2014 USD ($)
Segment Reporting, Revenue Reconciling Item [Line Items]
Number of Reportable Insurance Business Segments | segment				2
Net earned premiums		$ 4,364	$ 4,888	$ 8,796	$ 9,742
Net investment income		777	843	1,559	1,670
Other income		19	5	18	10
Total revenues		5,287	5,838	10,513	11,478
Other non-operating income (loss)		6	(11)	(12)	(20)
Realized investment gains (losses), non-operating	[1]	104	92	100	36
Gain (loss) on change in fair value of derivative, interest rate component, operating		23	10	40	20
Aflac Japan
Segment Reporting, Revenue Reconciling Item [Line Items]
Net earned premiums		2,978	3,578	6,056	7,138
Net investment income		605	680	1,218	1,343
Other income		7	8	15	17
Total revenues		3,590	4,266	7,289	8,498
Aflac U.S.
Segment Reporting, Revenue Reconciling Item [Line Items]
Net earned premiums		1,331	1,311	2,670	2,605
Net investment income		168	161	334	322
Other income		2	1	5	1
Total revenues		1,501	1,473	3,009	2,928
Other business segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Total revenues		65	10	91	20
Total Business Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Total revenues		5,156	5,749	10,389	11,446
Corporate
Segment Reporting, Revenue Reconciling Item [Line Items]
Total revenues		71	74	169	152
Intercompany eliminations
Segment Reporting, Revenue Reconciling Item [Line Items]
Total revenues		$ (50)	$ (66)	$ (133)	$ (136)

[1] Excluding a gain of $23 and $10 for the three-month periods and $40 and $20 for the six-month periods ended June 30, 2015, and 2014, 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