REINSURANCE - Effect of Reinsurance on Premiums and Benefits and Claims (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Effects of Reinsurance [Line Items]
Direct premium income	$ 4,464	$ 4,918	$ 13,426	$ 14,820
Net premium income	4,380	4,841	13,176	14,583
Direct benefits and claims	3,000	3,425	9,037	10,075
Benefits and claims, net	2,927	3,355	8,816	9,868
All other
Effects of Reinsurance [Line Items]
Ceded premiums	(10)	(10)	(28)	(30)
Assumed premiums earned	2	3	6	8
Ceded benefits and claims	8	(9)	12	(22)
Assumed benefits and claims	(12)	2	(29)	7
Aflac Japan
Effects of Reinsurance [Line Items]
Net premium income	2,980	3,534	9,036	10,672
Aflac Japan | Closed Block
Effects of Reinsurance [Line Items]
Ceded premiums	(130)	(70)	(352)	(215)
Assumed premiums earned	54	0	124	0
Ceded benefits and claims	(119)	(63)	(320)	(192)
Assumed benefits and claims	$ 50	$ 0	$ 116	$ 0