REINSURANCE - Effect of Reinsurance on Premiums and Benefits and Claims (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2017	Mar. 31, 2016
Effects of Reinsurance [Line Items]
Direct premium income	$ 4,724	$ 4,690
Net premium income	4,638	4,602
Direct benefits and claims	3,129	3,103
Benefits and claims, net	3,052	3,025
All other
Effects of Reinsurance [Line Items]
Ceded premiums	(12)	(12)
Assumed premiums earned	2	2
Ceded benefits and claims	(11)	(10)
Assumed benefits and claims from other companies	2	0
Aflac Japan
Effects of Reinsurance [Line Items]
Net premium income	3,194	3,179
Aflac Japan \| Closed Block
Effects of Reinsurance [Line Items]
Ceded premiums	(130)	(134)
Assumed premiums earned	54	56
Ceded benefits and claims	(122)	(121)
Assumed benefits and claims from other companies	54	53
Intercompany eliminations
Effects of Reinsurance [Line Items]
Ceded benefits and claims	13	14
Assumed benefits and claims from other companies	$ (13)	$ (14)

Amount of earned premiums assumed from other entities.

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