REINSURANCE Effect of Reinsurance on Premiums and Benefits and Claims (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Effects of Reinsurance [Line Items]
Direct premiums earned									$ 19,592	$ 17,904	$ 19,412
Ceded premiums									(608)	(520)	(350)
Assumed premiums earned									241	186	10
Net premium income	$ 4,778	$ 5,022	$ 4,823	$ 4,602	$ 4,394	$ 4,380	$ 4,364	$ 4,432	19,225	17,570	19,072
Direct benefits and claims									13,240	12,041
Benefits and claims, net									12,919	11,746	12,937
All other
Effects of Reinsurance [Line Items]
Ceded premiums									(48)	(39)
Assumed premiums earned									7	8
Ceded benefits and claims									(38)	(30)
Assumed benefits and claims from other companies									4	5
Aflac Japan
Effects of Reinsurance [Line Items]
Net premium income									13,537	12,046	13,861
Benefits and claims, net									9,828	8,705	$ 10,084
Aflac Japan | Closed block
Effects of Reinsurance [Line Items]
Ceded premiums									(560)	(481)
Assumed premiums earned									234	178
Ceded benefits and claims									(509)	(437)
Assumed benefits and claims from other companies									222	167
Intercompany eliminations
Effects of Reinsurance [Line Items]
Ceded benefits and claims									58	46
Assumed benefits and claims from other companies									$ (58)	$ (46)