REINSURANCE - Effect of Reinsurance on Premiums and Benefits and Claims (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Effects of Reinsurance [Line Items]
Direct premium income	$ 4,915	$ 4,448	$ 9,605	$ 8,962
Net premium income	4,823	4,364	9,425	8,796
Direct benefits and claims	3,332	3,013	6,435	6,038
Benefits and claims, net	3,254	2,937	6,279	5,889
All other
Effects of Reinsurance [Line Items]
Ceded premiums	(12)	(8)	(24)	(18)
Assumed premiums earned	2	1	4	4
Ceded benefits and claims	8	10	12	3
Assumed benefits and claims from other companies	(13)	(17)	(27)	(17)
Aflac Japan
Effects of Reinsurance [Line Items]
Net premium income	3,402	2,978	6,581	6,056
Aflac Japan \| Closed Block
Effects of Reinsurance [Line Items]
Ceded premiums	(141)	(132)	(275)	(222)
Assumed premiums earned	59	55	115	70
Ceded benefits and claims	(129)	(120)	(250)	(200)
Assumed benefits and claims from other companies	$ 56	$ 51	$ 109	$ 65

Amount of earned premiums assumed from other entities.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 235
-Section S99
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Amount of earned premiums ceded to other entities.

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Amount, before premiums ceded to other entities and premiums assumed by the entity, of premiums earned.

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Amount, before effect of policies assumed or ceded, of expense related to provision for policy benefits and costs incurred.

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Amount of reduction of provision for policy benefits and costs incurred for policies ceded.

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