REINSURANCE - Effect of Reinsurance on Premiums and Benefits and Claims (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2016	Mar. 31, 2015
Effects of Reinsurance [Line Items]
Direct premium income	$ 4,690	$ 4,514
Net premium income	4,602	4,432
Direct benefits and claims	3,103	3,025
Benefits and claims, net	3,025	2,952
All other
Effects of Reinsurance [Line Items]
Ceded premiums	(12)	(10)
Assumed premiums earned	2	3
Ceded benefits and claims	4	(7)
Assumed benefits and claims from other companies	(14)	0
Aflac Japan
Effects of Reinsurance [Line Items]
Net premium income	3,179	3,078
Aflac Japan \| Closed Block
Effects of Reinsurance [Line Items]
Ceded premiums	(134)	(90)
Assumed premiums earned	56	15
Ceded benefits and claims	(121)	(80)
Assumed benefits and claims from other companies	$ 53	$ 14

Amount of earned premiums assumed from other entities.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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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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