REINSURANCE Effect of Reinsurance on Premiums and Benefits and Claims (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Effects of Reinsurance [Line Items]
Direct premiums earned									$ 17,904	$ 19,412	$ 20,233
Ceded premiums									(520)	(350)	(110)
Assumed premiums earned									186	10	12
Net premium income	$ 4,394	$ 4,380	$ 4,364	$ 4,432	$ 4,489	$ 4,841	$ 4,888	$ 4,854	17,570	19,072	20,135
Direct benefits and claims									12,041	13,235
Benefits and claims, net									11,746	12,937	13,813
All other
Effects of Reinsurance [Line Items]
Ceded premiums									(39)	(39)
Assumed premiums earned									8	10
Ceded benefits and claims									16	(27)
Assumed benefits and claims from other companies									(41)	5
Aflac Japan
Effects of Reinsurance [Line Items]
Net premium income									12,046	13,861	14,982
Benefits and claims, net									8,705	10,084	$ 10,924
Aflac Japan | Closed block
Effects of Reinsurance [Line Items]
Ceded premiums									(481)	(311)
Assumed premiums earned									178	0
Ceded benefits and claims									(437)	(276)
Assumed benefits and claims from other companies									$ 167	$ 0