REINSURANCE - Effect of Reinsurance on Premiums and Benefits and Claims (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Effects of Reinsurance [Line Items]
Direct premium income	$ 4,448	$ 4,969	$ 8,962	$ 9,902
Net premium income	4,364	4,888	8,796	9,742
Direct benefits and claims	3,013	3,361	6,038	6,650
Benefits and claims, net	2,937	3,293	5,889	6,513
All other
Effects of Reinsurance [Line Items]
Ceded premiums	(8)	(11)	(18)	(20)
Assumed premiums earned	1	2	4	5
Ceded benefits and claims	10	(6)	3	(13)
Assumed benefits and claims	(17)	3	(17)	5
Aflac Japan
Effects of Reinsurance [Line Items]
Net premium income	2,978	3,578	6,056	7,138
Aflac Japan | Closed Block
Effects of Reinsurance [Line Items]
Ceded premiums	(132)	(72)	(222)	(145)
Assumed premiums earned	55	0	70	0
Ceded benefits and claims	(120)	(65)	(200)	(129)
Assumed benefits and claims	$ 51	$ 0	$ 65	$ 0